Faculty Publications: September, 2018

Query Results from the Smithsonian/NASA Astrophysics Data System (ADS)

The following are Harvard Physics faculty members' publications, added to the ADS database last month. Please note that some publications which appeared in print last month may not be included in the database (and therefore may not appear on this list) until the following month.

Title:
An Analytical Portrait of Binary Mergers in Hierarchical Triple Systems
Authors:
Randall, Lisa; Xianyu, Zhong-Zhi
Publication:
The Astrophysical Journal, Volume 864, Issue 2, article id. 134, 19 pp. (2018). (ApJ Homepage)
Publication Date:
09/2018
Origin:
IOP
Astronomy Keywords:
binaries: close, gravitational waves
DOI:
10.3847/1538-4357/aad7fe
Bibliographic Code:
2018ApJ...864..134R

Abstract

With better statistics and precision, eccentricity could prove to be a useful tool for understanding the origin and environment of binary black holes. Hierarchical triples in particular, which might be abundant in globular clusters and galactic nuclei, could generate observably large eccentricity at LIGO and future gravitational wave detectors. Measuring the eccentricity distribution accurately could help us probe the background and the formation of the mergers. In this paper we continue our previous investigation and improve our semianalytical description of the eccentricity distribution of mergers of hierarchical triple systems. Our result, which further reduces the reliance on numerical simulations, could be useful for statistically distinguishing different formation channels of observed binary mergers.

 

Title:
Nonlocal Optical Interferometry with Quantum Networks
Authors:
Khabiboulline, Emil T.; Borregaard, Johannes; De Greve, Kristiaan; Lukin, Mikhail D.
Publication:
eprint arXiv:1809.01659
Publication Date:
09/2018
Origin:
ARXIV
Keywords:
Quantum Physics, Astrophysics - Instrumentation and Methods for Astrophysics
Comment:
6 + 6 pages, 3 + 1 figures
Bibliographic Code:
2018arXiv180901659K

Abstract

We propose a method for optical interferometry in telescope arrays assisted by quantum networks. In our approach, the quantum state of incoming photons along with an arrival time index is stored in a binary qubit code at each receiver. Nonlocal retrieval of the quantum state via entanglement-assisted parity checks at the expected photon arrival rate allows for direct extraction of phase difference, effectively circumventing transmission losses between nodes. Compared to prior proposals, our scheme, based on efficient quantum data compression, offers an exponential decrease in required entanglement bandwidth. Experimental implementation is then feasible with near-term technology, enabling optical imaging of astronomical objects akin to well-established radio interferometers and pushing resolution beyond what is practically achievable classically.

 

Title:
Topological Superconductivity in a Phase-Controlled Josephson Junction
Authors:
Ren, Hechen; Pientka, Falko; Hart, Sean; Pierce, Andrew; Kosowsky, Michael; Lunczer, Lukas; Schlereth, Raimund; Scharf, Benedikt; Hankiewicz, Ewelina M.; Molenkamp, Laurens W.; Halperin, Bertrand I.; Yacoby, Amir
Publication:
eprint arXiv:1809.03076
Publication Date:
09/2018
Origin:
ARXIV
Keywords:
Condensed Matter - Mesoscale and Nanoscale Physics
Comment:
Supplementary contains resized figures. Original files are available upon request
Bibliographic Code:
2018arXiv180903076R

Abstract

Topological superconductors can support localized Majorana states at their boundaries. These quasi-particle excitations have non-Abelian statistics that can be used to encode and manipulate quantum information in a topologically protected manner. While signatures of Majorana bound states have been observed in one-dimensional systems, there is an ongoing effort to find alternative platforms that do not require fine-tuning of parameters and can be easily scalable to large numbers of states. Here we present a novel experimental approach towards a two-dimensional architecture. Using a Josephson junction made of HgTe quantum well coupled to thin-film aluminum, we are able to tune between a trivial and a topological superconducting state by controlling the phase difference $\phi$ across the junction and applying an in-plane magnetic field. We determine the topological state of the induced superconductor by measuring the tunneling conductance at the edge of the junction. At low magnetic fields, we observe a minimum in the tunneling spectra near zero bias, consistent with a trivial superconductor. However, as the magnetic field increases, the tunneling conductance develops a zero-bias peak which persists over a range of $\phi$ that expands systematically with increasing magnetic fields. Our observations are consistent with theoretical predictions for this system and with full quantum mechanical numerical simulations performed on model systems with similar dimensions and parameters. Our work establishes this system as a promising platform for realizing topological superconductivity and for creating and manipulating Majorana modes and will therefore open new avenues for probing topological superconducting phases in two-dimensional systems.

 

Title:
Quantum-Assisted Telescope Arrays
Authors:
Khabiboulline, Emil T.; Borregaard, Johannes; De Greve, Kristiaan; Lukin, Mikhail D.
Publication:
eprint arXiv:1809.03396
Publication Date:
09/2018
Origin:
ARXIV
Keywords:
Quantum Physics, Astrophysics - Instrumentation and Methods for Astrophysics
Comment:
9 pages, 8 figures
Bibliographic Code:
2018arXiv180903396K

Abstract

Quantum networks provide a platform for astronomical interferometers capable of imaging faint stellar objects. In a recent work [arXiv:1809.01659], we presented a protocol that circumvents transmission losses with efficient use of quantum resources and modest quantum memories. Here, we analyze a number of extensions to that scheme. We show that it can be operated as a truly broadband interferometer and generalized to multiple sites in the array. We also analyze how imaging based on the quantum Fourier transform provides improved signal-to-noise ratio compared to classical processing. Finally, we discuss physical realizations including photon detection-based quantum state transfer.

 

Title:
Spatial control of irreversible protein aggregation
Authors:
Weber, Christoph A.; Michaels, Thomas C. T.; Mahadevan, L.
Publication:
eprint arXiv:1809.03472
Publication Date:
09/2018
Origin:
ARXIV
Keywords:
Physics - Biological Physics, Condensed Matter - Soft Condensed Matter, Quantitative Biology - Subcellular Processes
Bibliographic Code:
2018arXiv180903472W

Abstract

Liquid cellular compartments spatially segregate from the cytoplasm and can regulate aberrant protein aggregation, a process linked to several medical conditions, including Alzheimer's and Parkinson's diseases. Yet the mechanisms by which these droplet-like compartments affect protein aggregation remain unknown. Here, we combine kinetic theory of protein aggregation and liquid-liquid phase separation to study the spatial control of irreversible protein aggregation in the presence of liquid compartments. We find that, even for weak interactions between the compartment constituents and the aggregating monomers, aggregates are strongly enriched inside the liquid compartment relative to the surrounding cytoplasm. We show that this enrichment is caused by a positive feedback mechanism of aggregate nucleation and growth which is mediated by a flux maintaining the phase equilibrium between the compartment and the cytoplasm. Our model predicts that the compartment volume that maximizes aggregate enrichment in the compartment is determined by the reaction orders of aggregate nucleation. The underlying mechanism of aggregate enrichment could be used to confine cytotoxic protein aggregates inside droplet-like compartments suggesting potential new avenues against aberrant protein aggregation. Our findings could also represent a common mechanism for the spatial control of irreversible chemical reactions in general.

 

Title:
Quantum Simulation and Optimization in Hot Quantum Networks
Authors:
Schuetz, Martin J. A.; Vermersch, Benoît; Kirchmair, Gerhard; Vandersypen, Lieven M. K.; Cirac, J. Ignacio; Lukin, Mikhail D.; Zoller, Peter
Publication:
eprint arXiv:1809.03794
Publication Date:
09/2018
Origin:
ARXIV
Keywords:
Quantum Physics, Condensed Matter - Mesoscale and Nanoscale Physics
Comment:
Manuscript: 5 pages, 4 figures. Supplementary Material: 14 pages, 5 figures
Bibliographic Code:
2018arXiv180903794S

Abstract

We propose and analyze a setup based on (solid-state) qubits coupled to a common multi-mode transmission line, which allows for coherent spin-spin interactions over macroscopic on-chip distances, without any ground-state cooling requirements for the data bus. Our approach allows for the realization of fast deterministic quantum gates between distant qubits, the simulation of quantum spin models with engineered (long-range) interactions, and provides a flexible architecture for the implementation of quantum approximate optimization algorithms.

 

Title:
Notes on the Onset of Clustering in Gas-Solid HCS
Authors:
Fullmer, William D.; Li, Xiaoqi; Yin, Xiaolong; Hrenya, Christine M.
Publication:
eprint arXiv:1809.04173
Publication Date:
09/2018
Origin:
ARXIV
Keywords:
Physics - Fluid Dynamics
Bibliographic Code:
2018arXiv180904173F

Abstract

This study contributes to the body of work on instabilities in the homogeneous cooling system focusing on clustering in the multiphase gas-particle system. The critical system size for the onset of instability, $L^*_c$, is studied via three different numerical methods: i) particle resolved direct numerical simulation; ii) computational fluid dynamics-discrete element method; and iii) a two-fluid model derived from kinetic theory. In general, the $L^*_c$ results at several concentrations, inelasticities and initial thermal Reynolds numbers are in good qualitative agreement with one another. Additionally, most of the expected trends (i.e., general $L^*_c (\phi)$ behavior) are observed. However, there is a larger level of quantitative discrepancy between the continuum and discrete particle methods than observed previous (simpler) granular results. While the level of agreement may be expected to decrease with the increased physical complexity of the gas-solid system, a significant time-dependence is revealed and shown to be responsible for some of the oddities in the numerical data.

 

Title:
Hybrid Architecture for Engineering Magnonic Quantum Networks
Authors:
Rusconi, C. C.; Schuetz, M. J. A.; Gieseler, J.; Lukin, M. D.; Romero-Isart, O.
Publication:
eprint arXiv:1809.04901
Publication Date:
09/2018
Origin:
ARXIV
Keywords:
Quantum Physics, Condensed Matter - Mesoscale and Nanoscale Physics
Comment:
Manuscript: 4 pages, 3 figures. Supplemental Material: 9 pages, 4 figures
Bibliographic Code:
2018arXiv180904901R

Abstract

We theoretically show that a network of superconducting loops and magnetic particles can be used to implement magnonic crystals with tunable magnonic band structures. In our approach, the loops mediate interactions between the particles and allow magnetic excitations to tunnel over long distances. As a result, different arrangements of loops and particles allow one to engineer the band structure for the magnonic excitations. We demonstrate that magnons can serve as a quantum bus for long-distance magnetic coupling of spin qubits. The qubits are coupled efficiently to the magnets in the network by their local magnetic-dipole interaction and provide an integrated way to measure the state of the magnonic quantum network.

 

Title:
Computational complexity of the Rydberg blockade in two dimensions
Authors:
Pichler, Hannes; Wang, Sheng-Tao; Zhou, Leo; Choi, Soonwon; Lukin, Mikhail D.
Publication:
eprint arXiv:1809.04954
Publication Date:
09/2018
Origin:
ARXIV
Keywords:
Quantum Physics, Condensed Matter - Quantum Gases, Computer Science - Computational Complexity, Physics - Atomic Physics
Comment:
12 pages, see also companion paper arXiv:1808.10816
Bibliographic Code:
2018arXiv180904954P

Abstract

We discuss the computational complexity of finding the ground state of the two-dimensional array of quantum bits that interact via strong van der Waals interactions. Specifically, we focus on systems where the interaction strength between two spins depends only on their relative distance $x$ and decays as $1/x^6$ that have been realized with individually trapped homogeneously excited neutral atoms interacting via the so-called Rydberg blockade mechanism. We show that the solution to NP-complete problems can be encoded in ground state of such a many-body system by a proper geometrical arrangement of the atoms. We present a reduction from the NP-complete maximum independent set problem on planar graphs with maximum degree three. Our results demonstrate that computationally hard optimization problems can be naturally addressed with coherent quantum optimizers accessible in near term experiments.

 

Title:
Probing quantum critical dynamics on a programmable Rydberg simulator
Authors:
Keesling, Alexander; Omran, Ahmed; Levine, Harry; Bernien, Hannes; Pichler, Hannes; Choi, Soonwon; Samajdar, Rhine; Schwartz, Sylvain; Silvi, Pietro; Sachdev, Subir; Zoller, Peter; Endres, Manuel; Greiner, Markus; Vuletic, Vladan; Lukin, Mikhail D.
Publication:
eprint arXiv:1809.05540
Publication Date:
09/2018
Origin:
ARXIV
Keywords:
Quantum Physics, Condensed Matter - Quantum Gases, Physics - Atomic Physics
Bibliographic Code:
2018arXiv180905540K

Abstract

Quantum phase transitions (QPTs) involve transformations between different states of matter that are driven by quantum fluctuations. These fluctuations play a dominant role in the quantum critical region surrounding the transition point, where the dynamics are governed by the universal properties associated with the QPT. The resulting quantum criticality has been explored by probing linear response for systems near thermal equilibrium. While time dependent phenomena associated with classical phase transitions have been studied in various scientific fields, understanding critical real-time dynamics in isolated, non-equilibrium quantum systems is of fundamental importance both for exploring novel approaches to quantum information processing and realizing exotic new phases of matter. Here, we use a Rydberg atom quantum simulator with programmable interactions to study the quantum critical dynamics associated with several distinct QPTs. By studying the growth of spatial correlations while crossing the QPT at variable speeds, we experimentally verify the quantum Kibble-Zurek mechanism (QKZM) for an Ising-type QPT, explore scaling universality, and observe corrections beyond simple QKZM predictions. This approach is subsequently used to investigate novel QPTs associated with chiral clock model providing new insights into exotic systems, and opening the door for precision studies of critical phenomena and applications to quantum optimization.

 

Title:
Latent Space Optimal Transport for Generative Models
Authors:
Liu, Huidong; Guo, Yang; Lei, Na; Shu, Zhixin; Yau, Shing-Tung; Samaras, Dimitris; Gu, Xianfeng
Publication:
eprint arXiv:1809.05964
Publication Date:
09/2018
Origin:
ARXIV
Keywords:
Computer Science - Machine Learning, Statistics - Machine Learning
Bibliographic Code:
2018arXiv180905964L

Abstract

Variational Auto-Encoders enforce their learned intermediate latent-space data distribution to be a simple distribution, such as an isotropic Gaussian. However, this causes the posterior collapse problem and loses manifold structure which can be important for datasets such as facial images. A GAN can transform a simple distribution to a latent-space data distribution and thus preserve the manifold structure, but optimizing a GAN involves solving a Min-Max optimization problem, which is difficult and not well understood so far. Therefore, we propose a GAN-like method to transform a simple distribution to a data distribution in the latent space by solving only a minimization problem. This minimization problem comes from training a discriminator between a simple distribution and a latent-space data distribution. Then, we can explicitly formulate an Optimal Transport (OT) problem that computes the desired mapping between the two distributions. This means that we can transform a distribution without solving the difficult Min-Max optimization problem. Experimental results on an eight-Gaussian dataset show that the proposed OT can handle multi-cluster distributions. Results on the MNIST and the CelebA datasets validate the effectiveness of the proposed method.

 

Title:
Graphene Transistor Based on Tunable Dirac-Fermion-Optics
Authors:
Wang, Ke; Elahi, Mirza M.; Masum Habib, K. M.; Taniguchi, Takashi; Watanabe, Kenji; Ghosh, Avik W.; Lee, Gil-Ho; Kim, Philip
Publication:
eprint arXiv:1809.06757
Publication Date:
09/2018
Origin:
ARXIV
Keywords:
Condensed Matter - Mesoscale and Nanoscale Physics
Comment:
27 pages, 9 figures
Bibliographic Code:
2018arXiv180906757W

Abstract

The linear energy-momentum dispersion, coupled with pseudo-spinors, makes graphene an ideal solid-state material platform to realize an electronic device based on Dirac-Fermionic relativistic quantum mechanics. Employing local gate control, several examples of electronic devices based on Dirac fermion dynamics have been demonstrated, including Klein tunneling, negative refraction and specular Andreev reflection. In this work, we present a quantum switch based on analogous Dirac-fermion-optics (DFO), in which the angle dependence of Klein tunneling is explicitly utilized to build tunable collimators and reflectors for the quantum wave function of Dirac fermions. We employ a novel dual-source design with a single flat reflector, which minimizes diffusive edge scattering and suppresses the background incoherent transmission. Our gate-tunable collimator-reflector device design enables measurement of the net DFO contribution in the switching device operation. We measure a full set of transmission coefficients of DFO wavefunction between multiple leads of the device, separating the classical contribution from that of any disorder in the channel. Since the DFO quantum switch demonstrated in this work requires no explicit energy gap, the switching operation is expected to be robust against thermal fluctuations and inhomogeneity length scales comparable to the Fermi wavelength. We find our quantum switch works at an elevated temperature up to 230 K and large bias current density up to 102 A/m, over a wide range of carrier densities. The tunable collimator-reflector coupled with the conjugated source electrodes developed in this work provides an additional component to build more efficient DFO electronic devices.

 

Title:
Sign reversing Hall effect in atomically thin high temperature superconductors
Authors:
Zhao, S. Y. Frank; Poccia, Nicola; Panetta, Margaret G.; Yu, Cyndia; Johnson, Jedediah W.; Yoo, Hyobin; Zhong, Ruidan; Gu, G. D.; Watanabe, Kenji; Taniguchi, Takashi; Postolova, Svetlana V.; Vinokur, Valerii M.; Kim, Philip
Publication:
eprint arXiv:1809.06944
Publication Date:
09/2018
Origin:
ARXIV
Keywords:
Condensed Matter - Superconductivity, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science, Condensed Matter - Strongly Correlated Electrons
Comment:
5 pages, 3 figures. Supplementary information is not included
Bibliographic Code:
2018arXiv180906944Z

Abstract

We fabricate van der Waals heterostructure devices using few unit cell thick Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ for magnetotransport measurements. The superconducting transition temperature and carrier density in atomically thin samples can be maintained to close to that of the bulk samples. As in the bulk sample, the sign of the Hall conductivity is found to be opposite to the normal state near the transition temperature but with a drastic enlargement of the region of Hall sign reversal in the temperature-magnetic field phase diagram as the thickness of samples decreases. Quantitative analysis of the Hall sign reversal based on the excess charge density in the vortex core and superconducting fluctuations suggests a renormalized superconducting gap in atomically thin samples at the 2-dimensional limit.

 

Title:
Spectrum, Landau-Zener theory and driven-dissipative dynamics of a staircase of photons
Authors:
Marino, J.; Shchadilova, Y. E.; Schleier-Smith, M.; Demler, E. A.
Publication:
eprint arXiv:1809.07332
Publication Date:
09/2018
Origin:
ARXIV
Keywords:
Condensed Matter - Quantum Gases, Quantum Physics
Comment:
10 pages, 7 figures
Bibliographic Code:
2018arXiv180907332M

Abstract

We study the production of photons in a model of three bosonic atomic modes non-linearly coupled to a cavity mode. In absence of external driving and dissipation, the energy levels at different photon numbers assemble into the steps of an energy staircase which can be employed as guidance for preparing multi-photon states. We consider adiabatic photon production, driving the system through a sequence of Landau-Zener transitions in the presence of external coherent light pumping. We also analyse the non-equilibrium dynamics of the system in the presence of competing coherent drive and cavity photon losses, and we find that the number of produced photons relaxes to a well-resolved metastable plateau before a dynamical instability, inherent to the type of light-matter coupling considered in the system, takes over, signalling a departure from the photons' steady state attained at intermediate times. We discuss the sensitivity of the time scales for the onset of this instability to system parameters and predict the metastable value of photons produced, solving the driven-dissipative dynamics including three-body correlations between light and matter degrees of freedom.

 

Title:
Homogenization of plasmonic crystals: Seeking the epsilon-near-zero effect
Authors:
Maier, Matthias; Mattheakis, Marios; Kaxiras, Efthimios; Luskin, Mitchell; Margetis, Dionisios
Publication:
eprint arXiv:1809.08276
Publication Date:
09/2018
Origin:
ARXIV
Keywords:
Mathematics - Numerical Analysis, Condensed Matter - Mesoscale and Nanoscale Physics, 35B27, 35Q60, 74Q10
Bibliographic Code:
2018arXiv180908276M

Abstract

By using an asymptotic analysis and numerical simulations, we derive and investigate a system of homogenized Maxwell's equations for conducting material sheets that are periodically arranged and embedded in a heterogeneous and anisotropic dielectric host. This structure is motivated by the need to design plasmonic crystals that enable the propagation of electromagnetic waves with no phase delay (epsilon-near-zero effect). Our microscopic model incorporates the surface conductivity of the two-dimensional (2D) material of each sheet and a corresponding line charge density through a line conductivity along possible edges of the sheets. Our analysis generalizes averaging principles inherent in previous Bloch-wave approaches. We investigate physical implications of our findings. In particular, we emphasize the role of the vector-valued corrector field, which expresses microscopic modes of surface waves on the 2D material. By using a Drude model for the surface conductivity of the sheet, we construct a Lorentzian function that describes the effective dielectric permittivity tensor of the plasmonic crystal as a function of frequency.

 

Title:
Polarization Whorls from M87 at the Event Horizon Telescope
Authors:
Gates, Delilah; Kapec, Daniel; Lupsasca, Alexandru; Shi, Yichen; Strominger, Andrew
Publication:
eprint arXiv:1809.09092
Publication Date:
09/2018
Origin:
ARXIV
Keywords:
High Energy Physics - Theory, Astrophysics - High Energy Astrophysical Phenomena, General Relativity and Quantum Cosmology
Comment:
19 pages, 2 figures
Bibliographic Code:
2018arXiv180909092G

Abstract

The Event Horizon Telescope (EHT) is expected to soon produce polarimetric images of the supermassive black hole at the center of the neighboring galaxy M87. This black hole is believed to be very rapidly spinning, within 2% of extremality. General relativity predicts that such a high-spin black hole has an emergent conformal symmetry near its event horizon. In this paper, we use this symmetry to analytically predict the polarized near-horizon emissions to be seen at the EHT and find a distinctive pattern of whorls aligned with the spin.

 

Title:
Topological Phononic Logic
Authors:
Pirie, Harris; Sadhuka, Shuvom; Wang, Jennifer; Hoffman, Jennifer E.
Publication:
eprint arXiv:1809.09187
Publication Date:
09/2018
Origin:
ARXIV
Keywords:
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Comment:
7 pages, 4 figures
Bibliographic Code:
2018arXiv180909187P

Abstract

Topological metamaterials have robust properties engineered from their macroscopic arrangement, rather than their microscopic constituency. They are promising candidates for creating next-generation technologies due to their protected dissipationless boundary modes. They can be designed by starting from Dirac metamaterials with either symmetry-enforced or accidental degeneracy. The latter case provides greater flexibility in the design of topological switches, waveguides, and cloaking devices, because a large number of tuning parameters can be used to break the degeneracy and induce a topological phase. However, the design of a topological logic element--a switch that can be controlled by the output of a separate switch--remains elusive. Here we numerically demonstrate a topological logic gate for ultrasound by exploiting the large phase space of accidental degeneracies in a honeycomb lattice. We find that a degeneracy can be broken by six physical parameters, and we show how to tune these parameters to create a phononic switch between a topological waveguide and a trivial insulator that can be triggered by ultrasonic heating. Our design scheme is directly applicable to photonic crystals and may guide the design of future electronic topological transistors.

 

Title:
Observation of the nonlinear Hall effect under time reversal symmetric conditions
Authors:
Ma, Qiong; Xu, Su-Yang; Shen, Huitao; Macneill, David; Fatemi, Valla; Mier Valdivia, Andres M.; Wu, Sanfeng; Chang, Tay-Rong; Du, Zongzheng; Hsu, Chuang-Han; Gibson, Quinn D.; Fang, Shiang; Kaxiras, Efthimios; Watanabe, Kenji; Taniguchi, Takashi; Cava, Robert J.; Lu, Hai-Zhou; Lin, Hsin; Fu, Liang; Gedik, Nuh; Jarillo-Herrero, Pablo
Publication:
eprint arXiv:1809.09279
Publication Date:
09/2018
Origin:
ARXIV
Keywords:
Condensed Matter - Mesoscale and Nanoscale Physics
Bibliographic Code:
2018arXiv180909279M

Abstract

The electrical Hall effect is the production of a transverse voltage under an out-of-plane magnetic field. Historically, studies of the Hall effect have led to major breakthroughs including the discoveries of Berry curvature and the topological Chern invariants. In magnets, the internal magnetization allows Hall conductivity in the absence of external magnetic field. This anomalous Hall effect (AHE) has become an important tool to study quantum magnets. In nonmagnetic materials without external magnetic fields, the electrical Hall effect is rarely explored because of the constraint by time-reversal symmetry. However, strictly speaking, only the Hall effect in the linear response regime, i.e., the Hall voltage linearly proportional to the external electric field, identically vanishes due to time-reversal symmetry. The Hall effect in the nonlinear response regime, on the other hand, may not be subject to such symmetry constraints. Here, we report the observation of the nonlinear Hall effect (NLHE) in the electrical transport of the nonmagnetic 2D quantum material, bilayer WTe2. Specifically, flowing an electrical current in bilayer WTe2 leads to a nonlinear Hall voltage in the absence of magnetic field. The NLHE exhibits unusual properties sharply distinct from the AHE in metals: The NLHE shows a quadratic I-V characteristic; It strongly dominates the nonlinear longitudinal response, leading to a Hall angle of about 90 degree. We further show that the NLHE directly measures the "dipole moment" of the Berry curvature, which arises from layer-polarized Dirac fermions in bilayer WTe2. Our results demonstrate a new Hall effect and provide a powerful methodology to detect Berry curvature in a wide range of nonmagnetic quantum materials in an energy-resolved way.

 

Title:
Thermal radiation and dissipative phase transition in a BEC with local loss
Authors:
Sels, Dries; Demler, Eugene
Publication:
eprint arXiv:1809.10516
Publication Date:
09/2018
Origin:
ARXIV
Keywords:
Quantum Physics, Condensed Matter - Quantum Gases
Bibliographic Code:
2018arXiv180910516S

Abstract

We study the dynamics of an atomic BEC subject to local dissipation in the form of atom losses. We show there is a critical loss rate at which the system undergoes a continuous dissipative phase transition from a homogenous state into a state which contains a sonic horizon. The latter drastically alters the behavior of the system by screening the drain. Dissipation leads to two types of fluctuations. First, fluctuations are generated by particles emitted in the reservoir. Both above and below the critical loss, these result in thermal emission of phonons with a temperature set by the loss rate and the chemical potential. The second type of fluctuation results from scattering on the drain and gives rise to a particular correlation pattern that can be observed in the density-density correlation. Aside from correlations between in an out scattered modes, outgoing particles are correlated with localized modes through a process that is reminiscent of Hawking radiation. Finally, we briefly discuss the dynamics of the system when there are two drains, in which case it is possible to construct a black hole laser.

 

Title:
Protein Motion and Configurations in a Form-Fitting Nanopore: Avidin in ClyA
Authors:
Lu, Bo; Stokes, Chris; Fahie, Monifa; Chen, Min; Golovchenko, Jene A.; Hau, Lene Vestergaard
Publication:
Biophysical Journal, vol. 115, issue 5, pp. 801-808
Publication Date:
09/2018
Origin:
CROSSREF
DOI:
10.1016/j.bpj.2018.07.024
Bibliographic Code:
2018BpJ...115..801L

Abstract

Not Available

Title:
Electrochemical stripping of cotton fabrics dyed with Reactive Black 5 in water and wastewater
Authors:
Ma, Xiangjuan; Wang, Xin; Yin, Xiaolin; Kan, Xiangru; Wang, Zeyuan
Publication:
Chemosphere, vol. 206, pp. 17-25
Publication Date:
09/2018
Origin:
CROSSREF
DOI:
10.1016/j.chemosphere.2018.04.122
Bibliographic Code:
2018Chmsp.206...17M

Abstract

We propose a greedy algorithm for the compression of Wannier functions into Gaussian-polynomials orbitals. The so-obtained compressed Wannier functions can be stored in a very compact form, and can be used to efficiently parameterize effective tight-binding Hamiltonians for multilayer 2D materials for instance. The compression method preserves the symmetries (if any) of the original Wannier function. We provide algorithmic details, and illustrate the performance of our implementation on several examples, including graphene, hexagonal boron-nitride, single-layer FeSe, and bulk silicon in the diamond cubic structure.

 

Title:
Dynamic flexoelectric effect on piezoelectric nanostructures
Authors:
Nguyen, B. H.; Nanthakumar, S. S.; Zhuang, X.; Wriggers, P.; Jiang, X.; Rabczuk, T.
Publication:
European Journal of Mechanics - A/Solids, vol. 71, pp. 404-409
Publication Date:
09/2018
Origin:
CROSSREF
DOI:
10.1016/j.euromechsol.2018.06.002
Bibliographic Code:
2018EJMS...71..404N

Abstract

Not Available

Title:
Prompt and non-prompt J/ψ and ψ (2S) suppression at high transverse momentum in 5.02 TeV Pb+Pb collisions with the ATLAS experiment
Authors:
Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2899 coauthors;
Publication:
The European Physical Journal C, Volume 78, Issue 9, article id. 762, 28 pp. (EPJC Homepage)
Publication Date:
09/2018
Origin:
SPRINGER
Abstract Copyright:
(c) 2018: CERN for the benefit of the ATLAS collaboration
DOI:
10.1140/epjc/s10052-018-6219-9
Bibliographic Code:
2018EPJC...78..762A

Abstract

A measurement of J/ψ and ψ (2S) production is presented. It is based on a data sample from Pb+Pb collisions at √{s_{NN}} = 5.02 TeV and pp collisions at √{s} = 5.02 TeV recorded by the ATLAS detector at the LHC in 2015, corresponding to an integrated luminosity of 0.42 nb^{-1} and 25 pb^{-1} in Pb+Pb and pp, respectively. The measurements of per-event yields, nuclear modification factors, and non-prompt fractions are performed in the dimuon decay channel for 9< pT^{μ μ } < 40 GeV in dimuon transverse momentum, and -2< y_{μ μ } < 2 in rapidity. Strong suppression is found in Pb+Pb collisions for both prompt and non-prompt J/ψ , increasing with event centrality. The suppression of prompt ψ (2S) is observed to be stronger than that of J/ψ , while the suppression of non-prompt ψ (2S) is equal to that of the non-prompt J/ψ within uncertainties, consistent with the expectation that both arise from b-quarks propagating through the medium. Despite prompt and non-prompt J/ψ arising from different mechanisms, the dependence of their nuclear modification factors on centrality is found to be quite similar.

 

Title:
Prompt and non-prompt J/ψ elliptic flow in Pb+Pb collisions at √{s_{_ {NN}}} = 5.02 Tev with the ATLAS detector
Authors:
Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2918 coauthors;
Publication:
The European Physical Journal C, Volume 78, Issue 9, article id. 784, 23 pp. (EPJC Homepage)
Publication Date:
09/2018
Origin:
SPRINGER
Abstract Copyright:
(c) 2018: CERN for the benefit of the ATLAS collaboration
DOI:
10.1140/epjc/s10052-018-6243-9
Bibliographic Code:
2018EPJC...78..784A

Abstract

The elliptic flow of prompt and non-prompt J/ψ was measured in the dimuon decay channel in Pb+Pb collisions at √{s_{_ {NN}}}=5.02 {TeV} with an integrated luminosity of 0.42 nb^{-1} with the ATLAS detector at the LHC. The prompt and non-prompt signals are separated using a two-dimensional simultaneous fit of the invariant mass and pseudo-proper decay time of the dimuon system from the J/ψ decay. The measurement is performed in the kinematic range of dimuon transverse momentum and rapidity 9<p_T<30 {GeV}, |y|<2, and 0-60% collision centrality. The elliptic flow coefficient, v_2, is evaluated relative to the event plane and the results are presented as a function of transverse momentum, rapidity and centrality. It is found that prompt and non-prompt J/ψ mesons have non-zero elliptic flow. Prompt J/ψ v_2 decreases as a function of p_T, while for non-prompt J/ψ it is, with limited statistical significance, consistent with a flat behaviour over the studied kinematic region. There is no observed dependence on rapidity or centrality.

 

Title:
Search for supersymmetry in final states with charm jets and missing transverse momentum in 13 TeV pp collisions with the ATLAS detector
Authors:
Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2893 coauthors;
Publication:
Journal of High Energy Physics, Volume 2018, Issue 9, article id. 50, 44 pp.
Publication Date:
09/2018
Origin:
SPRINGER
Keywords:
Hadron-Hadron scattering (experiments)
Abstract Copyright:
(c) 2018: The Author(s)
DOI:
10.1007/JHEP09(2018)050
Bibliographic Code:
2018JHEP...09..050A

Abstract

A search for supersymmetric partners of top quarks decaying as {\tilde{t}}_1\to c{\tilde{χ}}_1^0 and supersymmetric partners of charm quarks decaying as {\tilde{c}}_1\to c{\tilde{χ}}_1^0 , where {\tilde{χ}}_1^0 is the lightest neutralino, is presented. The search uses 36.1 fb-1 pp collision data at a centre-of-mass energy of 13 TeV collected by the ATLAS experiment at the Large Hadron Collider and is performed in final states with jets identified as containing charm hadrons. Assuming a 100% branching ratio to c{\tilde{χ}}_1^0 , top and charm squarks with masses up to 850 GeV are excluded at 95% confidence level for a massless lightest neutralino. For {m}_{{\tilde{t}}_1,{\tilde{c}}_1}-{m}_{{\tilde{χ}}_1^0} < 100 GeV, top and charm squark masses up to 500 GeV are excluded. [Figure not available: see fulltext.]

 

Title:
D-type fiber-base duality
Authors:
Haghighat, Babak; Kim, Joonho; Yan, Wenbin; Yau, Shing-Tung
Publication:
Journal of High Energy Physics, Volume 2018, Issue 9, article id. 60, 34 pp.
Publication Date:
09/2018
Origin:
SPRINGER
Keywords:
Brane Dynamics in Gauge Theories, Field Theories in Higher Dimensions, String Duality, Supersymmetric Gauge Theory
Abstract Copyright:
(c) 2018: The Author(s)
DOI:
10.1007/JHEP09(2018)060
Bibliographic Code:
2018JHEP...09..060H

Abstract

M5 branes probing D-type singularities give rise to 6d (1,0) SCFTs with SO × SO flavor symmetry known as D-type conformal matter theories. Gauging the diagonal SO-flavor symmetry leads to a little string theory with an intrinsic scale which can be engineered in F-theory by compactifying on a doubly-elliptic Calabi-Yau manifold. We derive Seiberg-Witten curves for these little string theories which can be interpreted as mirror curves for the corresponding Calabi-Yau manifolds. Under fiber-base duality these models are mapped to D-type quiver gauge theories and we check that their Seiberg-Witten curves match. By taking decompactification limits, we construct the curves for the related 6d SCFTs and connect to known results in the literature by further taking 5d and 4d limits.

 

Title:
Modular bootstrap revisited
Authors:
Collier, Scott; Lin, Ying-Hsuan; Yin, Xi
Publication:
Journal of High Energy Physics, Volume 2018, Issue 9, article id. 61, 31 pp.
Publication Date:
09/2018
Origin:
SPRINGER
Keywords:
AdS-CFT Correspondence, Black Holes, Conformal and W Symmetry, Conformal Field Theory
Abstract Copyright:
(c) 2018: The Author(s)
DOI:
10.1007/JHEP09(2018)061
Bibliographic Code:
2018JHEP...09..061C

Abstract

We constrain the spectrum of two-dimensional unitary, compact conformal field theories with central charge c > 1 using modular bootstrap. Upper bounds on the gap in the dimension of primary operators of any spin, as well as in the dimension of scalar primaries, are computed numerically as functions of the central charge using semi-definite programming. Our bounds refine those of Hellerman and Friedan-Keller, and are in some cases saturated by known CFTs. In particular, we show that unitary CFTs with c < 8 must admit relevant deformations, and that a nontrivial bound on the gap of scalar primaries exists for c < 25. We also study bounds on the dimension gap in the presence of twist gaps, bounds on the degeneracy of operators, and demonstrate how "extremal spectra" which maximize the degeneracy at the gap can be determined numerically.

 

Title:
Compactifications of ADE conformal matter on a torus
Authors:
Kim, Hee-Cheol; Razamat, Shlomo S.; Vafa, Cumrun; Zafrir, Gabi
Publication:
Journal of High Energy Physics, Volume 2018, Issue 9, article id. 110, 63 pp.
Publication Date:
09/2018
Origin:
SPRINGER
Keywords:
Duality in Gauge Field Theories, Field Theories in Higher Dimensions, Supersymmetric Gauge Theory
Abstract Copyright:
(c) 2018: The Author(s)
DOI:
10.1007/JHEP09(2018)110
Bibliographic Code:
2018JHEP...09..110K

Abstract

In this paper we study compactifications of ADE type conformal matter, N M5 branes probing ADE singularity, on torus with flux for global symmetry. We systematically construct the four dimensional theories by first going to five dimensions and studying interfaces. We claim that certain interfaces can be associated with turning on flux in six dimensions. The interface models when compactified on a circle comprise building blocks for constructing four dimensional models associated to flux compactifications of six dimensional theories on a torus. The theories in four dimensions turn out to be quiver gauge theories and the construction implies many interesting cases of IR symmetry enhancements and dualities of such theories.

 

Title:
Search for charged Higgs bosons decaying via H ± → τ ± ν τ in the τ+jets and τ+lepton final states with 36 fb-1 of pp collision data recorded at √{s}=13 TeV with the ATLAS experiment
Authors:
Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2917 coauthors;
Publication:
Journal of High Energy Physics, Volume 2018, Issue 9, article id. 139, 48 pp.
Publication Date:
09/2018
Origin:
SPRINGER
Keywords:
Beyond Standard Model, Hadron-Hadron scattering (experiments), Higgs physics
Abstract Copyright:
(c) 2018: The Author(s)
DOI:
10.1007/JHEP09(2018)139
Bibliographic Code:
2018JHEP...09..139A

Abstract

Charged Higgs bosons produced either in top-quark decays or in association with a top-quark, subsequently decaying via H ± → τ ± ν τ , are searched for in 36.1 fb-1 of proton-proton collision data at √{s}=13 TeV recorded with the ATLAS detector. Depending on whether the top-quark produced together with H ± decays hadronically or leptonically, the search targets τ+jets and τ+lepton final states, in both cases with a hadronically decaying τ-lepton. No evidence of a charged Higgs boson is found. For the mass range of {m}_{H^{± }} = 90-2000 GeV, upper limits at the 95% confidence level are set on the production cross-section of the charged Higgs boson times the branching fraction B(H^{±}\to {τ}^{± }{ν}_{τ}) in the range 4.2-0.0025 pb. In the mass range 90-160 GeV, assuming the Standard Model cross-section for t\overline{t} production, this corresponds to upper limits between 0.25% and 0.031% for the branching fraction B(t\to b{H}^{±})× B({H}^{±}\to {τ}^{± }{ν}_{τ}) . [Figure not available: see fulltext.]

 

Title:
Bootstrapping the spectral function: on the uniqueness of Liouville and the universality of BTZ
Authors:
Collier, Scott; Kravchuk, Petr; Lin, Ying-Hsuan; Yin, Xi
Publication:
Journal of High Energy Physics, Volume 2018, Issue 9, article id. 150, 43 pp.
Publication Date:
09/2018
Origin:
SPRINGER
Keywords:
Conformal and W Symmetry, Conformal Field Theory, Field Theories in Lower Dimensions, AdS-CFT Correspondence
Abstract Copyright:
(c) 2018: The Author(s)
DOI:
10.1007/JHEP09(2018)150
Bibliographic Code:
2018JHEP...09..150C

Abstract

We introduce spectral functions that capture the distribution of OPE coefficients and density of states in two-dimensional conformal field theories, and show that nontrivial upper and lower bounds on the spectral function can be obtained from semidefinite programming. We find substantial numerical evidence indicating that OPEs involving only scalar Virasoro primaries in a c > 1 CFT are necessarily governed by the structure constants of Liouville theory. Combining this with analytic results in modular bootstrap, we conjecture that Liouville theory is the unique unitary c > 1 CFT whose primaries have bounded spins. We also use the spectral function method to study modular constraints on CFT spectra, and discuss some implications of our results on CFTs of large c and large gap, in particular, to what extent the BTZ spectral density is universal.

 

Title:
New Pathway for Hot Electron Relaxation in Two-Dimensional Heterostructures
Authors:
Zhang, Jin; Hong, Hao; Zhang, Jia; Fu, Huixia; You, Peiwei; Lischner, Johannes; Liu, Kaihui; Kaxiras, Efthimios; Meng, Sheng
Affiliation:
AA( 0000-0001-7830-3464 ), AG( 0000-0002-8781-2495 ), AI( 0000-0002-1553-1432 )
Publication:
Nano Letters, vol. 18, issue 9, pp. 6057-6063
Publication Date:
09/2018
Origin:
CROSSREF
DOI:
10.1021/acs.nanolett.8b03005
Bibliographic Code:
2018NanoL..18.6057Z

Abstract

Not Available

 

Title:
Observation of Higgs boson production in association with a top quark pair at the LHC with the ATLAS detector
Authors:
Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2913 coauthors; Atlas Collaboration
Publication:
Physics Letters B, Volume 784, p. 173-191.
Publication Date:
09/2018
Origin:
ELSEVIER
Abstract Copyright:
(c) 2018 Elsevier Science B.V. All rights reserved.
DOI:
10.1016/j.physletb.2018.07.035
Bibliographic Code:
2018PhLB..784..173A

Abstract

The observation of Higgs boson production in association with a top quark pair (t t bar H), based on the analysis of proton-proton collision data at a centre-of-mass energy of 13 TeV recorded with the ATLAS detector at the Large Hadron Collider, is presented. Using data corresponding to integrated luminosities of up to 79.8 fb-1, and considering Higgs boson decays into b b bar , WW*, τ+τ-, γγ, and ZZ*, the observed significance is 5.8 standard deviations, compared to an expectation of 4.9 standard deviations. Combined with the t t bar H searches using a dataset corresponding to integrated luminosities of 4.5 fb-1 at 7 TeV and 20.3 fb-1 at 8 TeV, the observed (expected) significance is 6.3 (5.1) standard deviations. Assuming Standard Model branching fractions, the total t t bar H production cross section at 13 TeV is measured to be 670 ± 90 (stat.) -100+110 (syst.) fb, in agreement with the Standard Model prediction.

 

Title:
On the cosmological implications of the string Swampland
Authors:
Agrawal, Prateek; Obied, Georges; Steinhardt, Paul J.; Vafa, Cumrun
Publication:
Physics Letters B, Volume 784, p. 271-276.
Publication Date:
09/2018
Origin:
ELSEVIER
Abstract Copyright:
(c) 2018 Elsevier Science B.V. All rights reserved.
DOI:
10.1016/j.physletb.2018.07.040
Bibliographic Code:
2018PhLB..784..271A

Abstract

We study constraints imposed by two proposed string Swampland criteria on cosmology. These criteria involve an upper bound on the range traversed by scalar fields as well as a lower bound on |∇ϕ V | / V when V > 0. We find that inflationary models are generically in tension with these two criteria. Applying these same criteria to dark energy in the present epoch, we find that specific quintessence models can satisfy these bounds and, at the same time, satisfy current observational constraints. Assuming the two Swampland criteria are valid, we argue that the universe will undergo a phase transition within a few Hubble times. These criteria sharpen the motivation for future measurements of the tensor-to-scalar ratio r and the dark energy equation of state w, and for tests of the equivalence principle for dark matter.

 

Title:
Measurement of the Higgs boson mass in the H → ZZ* → 4ℓ and H → γγ channels with √{ s } = 13 TeV pp collisions using the ATLAS detector
Authors:
Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2900 coauthors; Atlas Collaboration
Publication:
Physics Letters B, Volume 784, p. 345-366.
Publication Date:
09/2018
Origin:
ELSEVIER
Abstract Copyright:
(c) 2018 Elsevier Science B.V. All rights reserved.
DOI:
10.1016/j.physletb.2018.07.050
Bibliographic Code:
2018PhLB..784..345A

Abstract

The mass of the Higgs boson is measured in the H → ZZ* → 4 ℓ and in the H → γγ decay channels with 36.1 fb-1 of proton-proton collision data from the Large Hadron Collider at a centre-of-mass energy of 13 TeV recorded by the ATLAS detector in 2015 and 2016. The measured value in the H → ZZ* → 4 ℓ channel is mHZZ* = 124.79 ± 0.37GeV, while the measured value in the H → γγ channel is mHγγ = 124.93 ± 0.40GeV. Combining these results with the ATLAS measurement based on 7 and 8 TeV proton-proton collision data yields a Higgs boson mass of mH = 124.97 ± 0.24GeV.

 

Title:
Quantum optics in Maxwell's fish eye lens with single atoms and photons
Authors:
Perczel, J.; Kómár, P.; Lukin, M. D.
Publication:
Physical Review A, Volume 98, Issue 3, id.033803 (PhRvA Homepage)
Publication Date:
09/2018
Origin:
APS
Abstract Copyright:
2018: American Physical Society
DOI:
10.1103/PhysRevA.98.033803
Bibliographic Code:
2018PhRvA..98c3803P

Abstract

We investigate the quantum optical properties of Maxwell's two-dimensional fish eye lens at the single-photon and single-atom level. We show that such a system mediates effectively infinite-range dipole-dipole interactions between atomic qubits, which can be used to entangle multiple pairs of distant qubits. We find that the rate of the photon exchange between two atoms, which are detuned from the cavity resonances, is well described by a model where the photon is focused to a diffraction-limited area during absorption. We consider the effect of losses on the system and study the fidelity of the entangling operation via dipole-dipole interaction. We derive our results analytically using perturbation theory and the Born-Markov approximation and then confirm their validity by numerical simulations. We also discuss how the two-dimensional Maxwell's fish eye lens could be realized experimentally using transformational plasmon optics.

 

Title:
Striking isotope effect on the metallization phase lines of liquid hydrogen and deuterium
Authors:
Zaghoo, Mohamed; Husband, Rachel J.; Silvera, Isaac F.
Publication:
Physical Review B, Volume 98, Issue 10, id.104102 (PhRvB Homepage)
Publication Date:
09/2018
Origin:
APS
Abstract Copyright:
2018: American Physical Society
DOI:
10.1103/PhysRevB.98.104102
Bibliographic Code:
2018PhRvB..98j4102Z

Abstract

Liquid atomic metallic hydrogen is the simplest, lightest, and most abundant of all liquid metals. The importance of nucleon motions or ion dynamics can be studied by comparing the metallization phase lines of the dissociative insulator-metal transitions of hydrogen and deuterium. We use static compression to study the optical properties of dense liquid metallic deuterium in the pressure region of 1.2-1.7 Mbars and measured temperatures up to ˜3000 K. At the same pressure (density) for the two isotopes, the phase lines of this transition reveal a prominent isotopic shift of ˜700 K. Our paper shows the importance of quantum nuclear effects in the metallization transition and conduction properties in dense hydrogen isotopes at conditions of giant planetary interiors and provides an invaluable benchmark for ab initio calculations.

 

Title:
Energetics and kinetics of vacancy defects in 4 H -SiC
Authors:
Kuate Defo, Rodrick; Zhang, Xingyu; Bracher, David; Kim, Gunn; Hu, Evelyn; Kaxiras, Efthimios
Publication Date:
09/2018
Origin:
APS
Abstract Copyright:
2018: American Physical Society
DOI:
10.1103/PhysRevB.98.104103
Bibliographic Code:
2018PhRvB..98j4103K

Abstract

Defect engineering in wide-gap semiconductors is important in controlling the performance of single-photon emitter devices. The effective incorporation of defects depends strongly on the ability to control their formation and location, as well as to mitigate attendant damage to the material. In this study, we combine density functional theory, molecular dyamics (MD), and kinetic Monte Carlo (KMC) simulations to study the energetics and kinetics of the silicon monovacancy VSi and related defects in 4 H -SiC. We obtain the defect formation energy for VSi in various charge states and use MD simulations to model the ion implantation process for creating defects. We also study the effects of high-temperature annealing on defect position and stability using KMC and analytical models. Using a larger (480-atom) supercell than previous studies, we obtain the temperature-dependent diffusivity of VSi in various charge states and find significantly lower barriers to diffusion than previous estimates. In addition, we examine the recombination with interstitial Si and conversion of VSi into CSiVC during annealing and propose methods for using strain to reduce changes in defect concentrations. Our results provide guidance for experimental efforts to control the position and density of VSi defects within devices, helping to realize their potential as solid-state qubits.

 

Title:
Berry curvature dipole current in the transition metal dichalcogenides family
Authors:
You, Jhih-Shih; Fang, Shiang; Xu, Su-Yang; Kaxiras, Efthimios; Low, Tony
Publication:
Physical Review B, Volume 98, Issue 12, id.121109 (PhRvB Homepage)
Publication Date:
09/2018
Origin:
APS
Abstract Copyright:
2018: American Physical Society
DOI:
10.1103/PhysRevB.98.121109
Bibliographic Code:
2018PhRvB..98l1109Y

Abstract

We study the quantum nonlinear Hall effect in two-dimensional (2D) materials with time-reversal symmetry. When only one mirror line exists, a transverse charge current occurs in the second-order response to an external electric field, as a result of the Berry curvature dipole in momentum space. Candidate 2D materials to observe this effect are two-dimensional transition metal dichalcogenides (TMDCs). First, we use an ab initio based tight-binding approach to demonstrate that monolayer Td-structure TMDCs exhibit a finite Berry curvature dipole. In the 1 H and 1 T' phase of TMDCs, we show the emergence of a finite Berry curvature dipole with the application of strain and an electrical displacement field, respectively.

 

Title:
Critical strange metal from fluctuating gauge fields in a solvable random model
Authors:
Patel, Aavishkar A.; Sachdev, Subir
Publication:
Physical Review B, Volume 98, Issue 12, id.125134 (PhRvB Homepage)
Publication Date:
09/2018
Origin:
APS
Abstract Copyright:
2018: American Physical Society
DOI:
10.1103/PhysRevB.98.125134
Bibliographic Code:
2018PhRvB..98l5134P

Abstract

Building upon techniques employed in the construction of the Sachdev-Ye-Kitaev model, which is a solvable (0 + 1)-dimensional model of a non-Fermi liquid, we develop a solvable infinite-ranged random-hopping model of fermions coupled to fluctuating U (1 ) gauge fields. In a specific large-N limit, our model realizes a gapless non-Fermi-liquid phase, which combines the effects of hopping and interaction terms. We derive the thermodynamic properties of the non-Fermi-liquid phase realized by this model and the charge transport properties of an infinite-dimensional version with spatial structure.

 

Title:
Readout of singlet-triplet qubits at large magnetic field gradients
Authors:
Orona, Lucas A.; Nichol, John M.; Harvey, Shannon P.; Bøttcher, Charlotte G. L.; Fallahi, Saeed; Gardner, Geoffrey C.; Manfra, Michael J.; Yacoby, Amir
Publication:
Physical Review B, Volume 98, Issue 12, id.125404 (PhRvB Homepage)
Publication Date:
09/2018
Origin:
APS
Abstract Copyright:
2018: American Physical Society
DOI:
10.1103/PhysRevB.98.125404
Bibliographic Code:
2018PhRvB..98l5404O

Abstract

Visibility of singlet-triplet qubit readout is reduced to almost zero in large magnetic field gradients due to relaxation processes. Here we present a new readout technique that is robust against relaxation and allows for measurement when previously studied methods fail. This technique maps the qubit onto spin states that are immune to relaxation using a spin-dependent electron tunneling process between the qubit and the lead. We probe this readout's performance as a function of magnetic field gradient and applied magnetic field, and optimize the pulse applied to the qubit through experiment and simulation.

 

Title:
Search for Higgs bosons produced via vector-boson fusion and decaying into bottom quark pairs in √{s }=13 TeV p p collisions with the ATLAS detector
Authors:
Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2914 coauthors. Atlas Collaboration
Publication:
Physical Review D, Volume 98, Issue 5, id.052003 (PhRvD Homepage)
Publication Date:
09/2018
Origin:
APS
Abstract Copyright:
2018: CERN
DOI:
10.1103/PhysRevD.98.052003
Bibliographic Code:
2018PhRvD..98e2003A

Abstract

A search for the b b ¯ decay of the Standard Model Higgs boson produced through vector-boson fusion is presented. Three mutually exclusive channels are considered: two all-hadronic channels and a photon-associated channel. Results are reported from the analysis of up to 30.6 fb-1 of p p data at √{s }=13 TeV collected with the ATLAS detector at the LHC. The measured signal strength relative to the Standard Model prediction from the combined analysis is 2. 5-1.3+1.4 for inclusive Higgs boson production and 3. 0-1.6+1.7 for vector-boson fusion production only.

 

Title:
Measurements of Higgs boson properties in the diphoton decay channel with 36 fb-1 of p p collision data at √{s }=13 TeV with the ATLAS detector
Authors:
Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2889 coauthors. Atlas Collaboration
Publication:
Physical Review D, Volume 98, Issue 5, id.052005 (PhRvD Homepage)
Publication Date:
09/2018
Origin:
APS
Abstract Copyright:
2018: CERN
DOI:
10.1103/PhysRevD.98.052005
Bibliographic Code:
2018PhRvD..98e2005A

Abstract

Properties of the Higgs boson are measured in the two-photon final state using 36.1 fb-1 of proton-proton collision data recorded at √{s }=13 TeV by the ATLAS experiment at the Large Hadron Collider. Cross-section measurements for the production of a Higgs boson through gluon-gluon fusion, vector-boson fusion, and in association with a vector boson or a top-quark pair are reported. The signal strength, defined as the ratio of the observed to the expected signal yield, is measured for each of these production processes as well as inclusively. The global signal strength measurement of 0.99 ±0.14 improves on the precision of the ATLAS measurement at √{s }=7 and 8 TeV by a factor of two. Measurements of gluon-gluon fusion and vector-boson fusion productions yield signal strengths compatible with the Standard Model prediction. Measurements of simplified template cross sections, designed to quantify the different Higgs boson production processes in specific regions of phase space, are reported. The cross section for the production of the Higgs boson decaying to two isolated photons in a fiducial region closely matching the experimental selection of the photons is measured to be 55 ±10 fb , which is in good agreement with the Standard Model prediction of 64 ±2 fb . Furthermore, cross sections in fiducial regions enriched in Higgs boson production in vector-boson fusion or in association with large missing transverse momentum, leptons or top-quark pairs are reported. Differential and double-differential measurements are performed for several variables related to the diphoton kinematics as well as the kinematics and multiplicity of the jets produced in association with a Higgs boson. These differential cross sections are sensitive to higher order QCD corrections and properties of the Higgs boson, such as its spin and C P quantum numbers. No significant deviations from a wide array of Standard Model predictions are observed. Finally, the strength and tensor structure of the Higgs boson interactions are investigated using an effective Lagrangian, which introduces additional C P -even and C P -odd interactions. No significant new physics contributions are observed.

 

Title:
Combination of searches for heavy resonances decaying into bosonic and leptonic final states using 36 fb-1 of proton-proton collision data at √{s }=13 TeV with the ATLAS detector
Authors:
Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2922 coauthors. Atlas Collaboration
Publication:
Physical Review D, Volume 98, Issue 5, id.052008 (PhRvD Homepage)
Publication Date:
09/2018
Origin:
APS
Abstract Copyright:
2018: CERN
DOI:
10.1103/PhysRevD.98.052008
Bibliographic Code:
2018PhRvD..98e2008A

Abstract

Searches for new heavy resonances decaying into different pairings of W , Z , or Higgs bosons, as well as directly into leptons, are presented using a data sample corresponding to 36.1 fb-1 of p p collisions at √{s }=13 TeV collected during 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider. Analyses selecting bosonic decay modes in the q q q q , ν ν q q , ℓν q q , ℓℓq q , ℓν ℓν , ℓℓν ν , ℓν ℓℓ, ℓℓℓℓ, q q b b , ν ν b b , ℓν b b , and ℓℓb b final states are combined, searching for a narrow-width resonance. Likewise, analyses selecting the leptonic ℓν and ℓℓ final states are also combined. These two sets of analyses are then further combined. No significant deviation from the Standard Model predictions is observed. Three benchmark models are tested: a model predicting the existence of a new heavy scalar singlet, a simplified model predicting a heavy vector-boson triplet, and a bulk Randall-Sundrum model with a heavy spin-2 Kaluza-Klein excitation of the graviton. Cross section limits are set at the 95% confidence level using an asymptotic approximation and are compared with predictions for the benchmark models. These limits are also expressed in terms of constraints on couplings of the heavy vector-boson triplet to quarks, leptons, and the Higgs boson. The data exclude a heavy vector-boson triplet with mass below 5.5 TeV in a weakly coupled scenario and 4.5 TeV in a strongly coupled scenario, as well as a Kaluza-Klein graviton with mass below 2.3 TeV.

 

Title:
Physical interpretation of the partition function for colloidal clusters
Authors:
Klein, Ellen D.; Perry, Rebecca W.; Manoharan, Vinothan N.
Publication:
Physical Review E, Volume 98, Issue 3, id.032608 (PhRvE Homepage)
Publication Date:
09/2018
Origin:
APS
Abstract Copyright:
2018: American Physical Society
DOI:
10.1103/PhysRevE.98.032608
Bibliographic Code:
2018PhRvE..98c2608K

Abstract

Colloidal clusters consist of small numbers of colloidal particles bound by weak short-range attractions. The equilibrium probability of observing a cluster in a particular geometry is well described by a statistical mechanical model originally developed for molecules. To explain why this model fits experimental data so well, we derive the partition function classically, with no quantum-mechanical considerations. Then, by comparing and contrasting the derivation in particle coordinates with that in center-of-mass coordinates, we physically interpret the terms in the center-of-mass formulation, which is equivalent to the high-temperature partition function for molecules. We discuss, from a purely classical perspective, how and why cluster characteristics such as the symmetry number, moments of inertia, and vibrational frequencies affect the equilibrium probabilities.

 

Title:
High-Fidelity Control and Entanglement of Rydberg-Atom Qubits
Authors:
Levine, Harry; Keesling, Alexander; Omran, Ahmed; Bernien, Hannes; Schwartz, Sylvain; Zibrov, Alexander S.; Endres, Manuel; Greiner, Markus; Vuletić, Vladan; Lukin, Mikhail D.
Publication:
Physical Review Letters, Volume 121, Issue 12, id.123603 (PhRvL Homepage)
Publication Date:
09/2018
Origin:
APS
Abstract Copyright:
2018: American Physical Society
DOI:
10.1103/PhysRevLett.121.123603
Bibliographic Code:
2018PhRvL.121l3603L

Abstract

Individual neutral atoms excited to Rydberg states are a promising platform for quantum simulation and quantum information processing. However, experimental progress to date has been limited by short coherence times and relatively low gate fidelities associated with such Rydberg excitations. We report progress towards high-fidelity quantum control of Rydberg-atom qubits. Enabled by a reduction in laser phase noise, our approach yields a significant improvement in coherence properties of individual qubits. We further show that this high-fidelity control extends to the multi-particle case by preparing a two-atom entangled state with a fidelity exceeding 0.97(3), and extending its lifetime with a two-atom dynamical decoupling protocol. These advances open up new prospects for scalable quantum simulation and quantum computation with neutral atoms.

 

Title:
Quantum Nonlinear Optics in Atomically Thin Materials
Authors:
Wild, Dominik S.; Shahmoon, Ephraim; Yelin, Susanne F.; Lukin, Mikhail D.
Publication:
Physical Review Letters, Volume 121, Issue 12, id.123606 (PhRvL Homepage)
Publication Date:
09/2018
Origin:
APS
Abstract Copyright:
2018: American Physical Society
DOI:
10.1103/PhysRevLett.121.123606
Bibliographic Code:
2018PhRvL.121l3606W

Abstract

We show that a nonlinear optical response associated with a resonant, atomically thin material can be dramatically enhanced by placing it in front of a partially reflecting mirror, rendering otherwise weakly nonlinear systems suitable for experiments and applications involving quantum nonlinear optics. Our approach exploits the nonlinear response of long-lived polariton resonances that arise at particular distances between the material and the mirror. The scheme is entirely based on free-space optics, eliminating the need for cavities or complex nanophotonic structures. We analyze a specific implementation based on exciton-polariton resonances in two-dimensional semiconductors and discuss the role of imperfections and loss.

 

Title:
Simultaneous Broadband Vector Magnetometry Using Solid-State Spins
Authors:
Schloss, Jennifer M.; Barry, John F.; Turner, Matthew J.; Walsworth, Ronald L.
Publication:
Physical Review Applied, Volume 10, Issue 3, id.034044
Publication Date:
09/2018
Origin:
APS
Abstract Copyright:
2018: American Physical Society
DOI:
10.1103/PhysRevApplied.10.034044
Bibliographic Code:
2018PhRvP..10c4044S

Abstract

We demonstrate a vector magnetometer that simultaneously measures all Cartesian components of a dynamic magnetic field using an ensemble of nitrogen-vacancy (NV) centers in a single-crystal diamond. Optical NV-diamond measurements provide high-sensitivity, broadband magnetometry under ambient or extreme physical conditions and the fixed crystallographic axes inherent to this solid-state system enable vector sensing free from heading errors. In the present device, multichannel lock-in detection extracts the magnetic-field-dependent spin-resonance shifts of NVs oriented along all four tetrahedral diamond axes from the optical signal measured on a single detector. The sensor operates from near dc (5 Hz) up to a 12.5-kHz measurement bandwidth and simultaneously achieves approximately 50 pT /√{Hz } magnetic-field sensitivity for each Cartesian component, which is, to date, the highest demonstrated sensitivity of a full vector magnetometer employing solid-state spins. Compared to optimized devices interrogating the four NV orientations sequentially, the simultaneous vector magnetometer enables a 4 × measurement speedup. This technique can be extended to pulsed-type sensing protocols and parallel wide-field magnetic imaging.

 

Title:
Nanoscale magnetic imaging using quantum defects in diamond
Authors:
Walsworth, Ronald L.
Affiliation:
AA(Harvard-Smithsonian Ctr. for Astrophysics (United States))
Publication:
Proceedings of the SPIE, Volume 10726, id. 107260U 7 pp. (2018).
Publication Date:
09/2018
Origin:
SPIE
Abstract Copyright:
(c) 2018: SPIE. Downloading of the abstract is permitted for personal use only.
Comment:
ISBN: 9781510620230
DOI:
10.1117/12.2323374
Bibliographic Code:
2018SPIE10726E..0UW

Abstract

Nitrogen vacancy (NV) quantum defects in diamond provide an unparalleled combination of magnetic field sensitivity and spatial resolution in a room-temperature solid, with wide-ranging applications in both the physical and life sciences. NVs can be brought into few nanometer proximity of magnetic field sources of interest, such as single proton and electron spins while maintaining long NV spin coherence times, a large ( Bohr magneton) Zeeman shift of the NV spin states, and optical preparation and readout of the NV spin. I will provide an overview of this nanoscale sensing technology and its diverse applications.


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