Faculty Publications: November, 2017

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:
Proposal for the Detection of Magnetic Monopoles in Spin Ice via Nanoscale Magnetometry
Authors:
Kirschner, Franziska K. K.; Flicker, Felix; Yacoby, Amir; Yao, Norman Y.; Blundell, Stephen J.
Publication:
eprint arXiv:1711.00408
Publication Date:
11/2017
Origin:
ARXIV
Keywords:
Condensed Matter - Strongly Correlated Electrons
Comment:
5 pages, 2 figures
Bibliographic Code:
2017arXiv171100408K

Abstract

We present a proposal for applying nanoscale magnetometry to the search for magnetic monopoles in the spin ice materials holmium and dysprosium titanate. Employing Monte Carlo simulations of the dipolar spin ice model, we find that when cooled to below $1.5\,$K these materials exhibit a sufficiently low monopole density to enable the direct observation of magnetic fields from individual monopoles. At these temperatures we demonstrate that noise spectroscopy can capture the intrinsic fluctuations associated with monopole dynamics, allowing one to isolate the qualitative effects associated with both the Coulomb interaction between monopoles and the topological constraints implied by Dirac strings. We describe in detail three different nanoscale magnetometry platforms (muon spin rotation, nitrogen vacancy defects, and nanoSQUID arrays) that can be used to detect monopoles in these experiments, and analyze the advantages of each.

 

Title:
From Bosonic Topological Transition to Symmetric Fermion Mass Generation
Authors:
You, Yi-Zhuang; He, Yin-Chen; Vishwanath, Ashvin; Xu, Cenke
Publication:
eprint arXiv:1711.00863
Publication Date:
11/2017
Origin:
ARXIV
Keywords:
Condensed Matter - Strongly Correlated Electrons
Comment:
15 pages + references, 6 figures
Bibliographic Code:
2017arXiv171100863Y

Abstract

The bosonic topological transition (BTT) is a quantum critical point between the bosonic symmetry protected topological phase and the trivial phase. In this work, we derive a description of this transition in terms of compact quantum electrodynamics (QED) with four fermion flavors ($N_f=4$). This allows us to describe the transition in a lattice model with the maximal microscopic symmetry: an internal SO(4) symmetry. Within a systematic renormalization group analysis, we identify the critical point with the desired O(4) emergent symmetry and all expected deformations. By lowering the microscopic symmetry we recover the previous $N_f=2$ non-compact QED description of the BTT. Finally, by merging two BTTs we recover a previously discussed theory of symmetric mass generation, as an SU(2) quantum chromodynamics-Higgs theory with $N_f=4$ flavors of SU(2) fundamental fermions and one SU(2) fundamental Higgs boson. This provides a consistency check on both theories.

 

Title:
The String Landscape, the Swampland, and the Missing Corner
Authors:
Brennan, T. Daniel; Carta, Federico; Vafa, Cumrun
Publication:
eprint arXiv:1711.00864
Publication Date:
11/2017
Origin:
ARXIV
Keywords:
High Energy Physics - Theory
Comment:
64 pages, 12 figures, 2 appendices; v2: additional references
Bibliographic Code:
2017arXiv171100864B

Abstract

We give a brief overview of the string landscape and techniques used to construct string compactifications. We then explain how this motivates the notion of the swampland and review a number of conjectures that attempt to characterize theories in the swampland. We also compare holography in the context of superstrings with the similar, but much simpler case of topological string theory. For topological strings, there is a direct definition of topological gravity based on a sum over a "quantum gravitational foam." In this context, holography is the statement of an identification between a gravity and gauge theory, both of which are defined independently of one another. This points to a missing corner in string dualities which suggests the search for a direct definition of quantum theory of gravity rather than relying on its strongly coupled holographic dual as an adequate substitute (Based on TASI 2017 lectures given by C. Vafa).

 

Title:
Intermittent behaviors in weakly coupled map lattices
Authors:
Li, Tiexiang; Lin, Wen-wei; Wang, Yiqian; Yau, Shing-Tung
Publication:
eprint arXiv:1711.01457
Publication Date:
11/2017
Origin:
ARXIV
Keywords:
Mathematics - Dynamical Systems, 37C40, 37C30, 37A25
Comment:
33 pages, 4 figures
Bibliographic Code:
2017arXiv171101457L

Abstract

In this paper, we study intermittent behaviors of coupled piecewise-expanding map lattices with two nodes and a weak coupling. We show that the successive phase transition between ordered and disordered phases occurs for almost every orbit. That is, we prove $\liminf_{n\rightarrow \infty}| x_1(n)-x_2(n)|=0$ and $\limsup_{n\rightarrow \infty}| x_1(n)-x_2(n)|\ge c_0>0$, where $x_1(n), x_2(n)$ correspond to the coordinates of two nodes at the iterative step $n$. We also prove the same conclusion for weakly coupled tent-map lattices with any multi-nodes.

 

Title:
Regularized lattice Boltzmann Multicomponent models for low Capillary and Reynolds microfluidics flows
Authors:
Montessori, Andrea; Lauricella, Marco; La Rocca, Michele; Succi, Sauro; Stolovicki, Elad; Ziblat, Roy; Weitz, David
Publication:
eprint arXiv:1711.02003
Publication Date:
11/2017
Origin:
ARXIV
Keywords:
Physics - Fluid Dynamics, Physics - Computational Physics, 76T10, 82B40
Comment:
9 pages, 5 figures
Bibliographic Code:
2017arXiv171102003M

Abstract

We present a regularized version of the color gradient lattice Boltzmann (LB) scheme for the simulation of droplet formation in microfluidic devices of experimental relevance. The regularized version is shown to provide computationally efficient access to Capillary number regimes relevant to droplet generation via microfluidic devices, such as flow-focusers and the more recent microfluidic step emulsifier devices.

 

Title:
Improved quantum sensing with a single solid-state spin via spin-to-charge conversion
Authors:
Jaskula, Jean-Christophe; Shields, Brendan J.; Bauch, Erik; Lukin, Mikhail. D.; Trifonov, Alexei S.; Walsworth, Ronald L.
Publication:
eprint arXiv:1711.02023
Publication Date:
11/2017
Origin:
ARXIV
Keywords:
Quantum Physics, Condensed Matter - Mesoscale and Nanoscale Physics
Comment:
11 pages
Bibliographic Code:
2017arXiv171102023J

Abstract

Efficient optical readout of a single, solid-state electronic spin at room temperature is a key challenge for nanoscale quantum sensing. Here we apply the technique of spin-to-charge conversion to enhance the optical spin-state readout of a single Nitrogen-Vacancy (NV) color center in room temperature diamond, with no degradation in the NV spin coherence time. We demonstrate an order-of-magnitude improvement in spin readout noise per shot and about a factor of five improvement in AC magnetometry sensitivity, compared to the conventional NV spin-state optical readout method. This improvement is realized in a widely-applicable bulk diamond system. We show that selecting for successful charge state initialization leads to possible further improvement in sensitivity. This technique is well suited to sensing applications involving low duty cycle pulsed signals, e.g., in biomagnetometry, where long deadtimes demand optimized sensitivity per shot.

 

Title:
Universal behavior of dispersive Dirac cone in plasmonic metamaterials
Authors:
Maier, Matthias; Mattheakis, Marios; Kaxiras, Efthimios; Luskin, Mitchell; Margetis, Dionisios
Publication:
eprint arXiv:1711.02210
Publication Date:
11/2017
Origin:
ARXIV
Keywords:
Physics - Optics
Bibliographic Code:
2017arXiv171102210M

Abstract

We demonstrate analytically and numerically that the dispersive Dirac cone emulating an epsilon-near-zero (ENZ) behavior is a universal property of plasmonic crystals consisting of 2D metals. Our starting point is a periodic array of two-dimensional metallic sheets embedded in an inhomogeneous and anisotropic dielectric host. By invoking a systematic bifurcation argument for arbitrary dielectric profiles, we show how transverse-magnetic Bloch waves experience an effective dielectric function that averages out microscopic details of the host medium. The corresponding effective dispersion relation reduces to a Dirac cone when the conductivity of the metallic sheet and the period of the array satisfy a critical condition for ENZ behavior. Our analytical findings are in excellent agreement with numerical simulations.

 

Title:
Tunneling Spectroscopy of Quantum Hall States in Bilayer Graphene PN Networks
Authors:
Wang, Ke; Harzheim, Achim; Lee, Ji Ung; Taniguchi, Takashi; Watanabe, Kenji; Kim, Philip
Publication:
eprint arXiv:1711.03184
Publication Date:
11/2017
Origin:
ARXIV
Keywords:
Condensed Matter - Mesoscale and Nanoscale Physics
Bibliographic Code:
2017arXiv171103184W

Abstract

Two dimensional electronic systems under strong magnetic field form quantum Hall (QH) edge states, which propagate along the boundary of a sample with a dissipationless current. Engineering the pathway of these propagating one-dimensional chiral modes enables the investigation of quantum tunneling between adjacent QH states. Here, we report tunneling transport in spatially controlled networks of QH edge states in bilayer graphene. We observe resonant tunneling between co-propagating QH edges across barriers formed by electrically defining incompressible strips. Employing spectroscopic tunneling measurements enable the direct probing of the spatial profile, density of states, and compressibility of the QH edge states with an unprecedented energy resolution. The capability to engineer the QH edge network provides an opportunity to build future quantum electronic devices supported by rich underline physics.

 

Title:
Heterointerface effects in the electro-intercalation of van der Waals heterostructures
Authors:
Kwabena Bediako, D.; Rezaee, Mehdi; Zhao, Shu Yang Frank; Taniguchi, Takashi; Watanabe, Kenji; Brower-Thomas, Tina L.; Kim, Philip
Publication:
eprint arXiv:1711.03465
Publication Date:
11/2017
Origin:
ARXIV
Keywords:
Condensed Matter - Materials Science
Comment:
8 pages, 5 Figures, Methods, and Supplementary Information
Bibliographic Code:
2017arXiv171103465K

Abstract

Molecular-scale manipulation of electronic/ionic charge accumulation in materials is a preeminent challenge, particularly in electrochemical energy storage. Layered van der Waals (vdW) crystals exemplify a diverse family of materials that permit ions to reversibly associate with a host atomic lattice by intercalation into interlamellar gaps. Motivated principally by the search for high-capacity battery anodes, ion intercalation in composites of vdW materials is a subject of intense study. Yet the precise role and ability of heterolayers to modify intercalation reactions remains elusive. Previous studies of vdW hybrids represented ensemble measurements at macroscopic films or powders, which do not permit the isolation and investigation of the chemistry at 2-dimensional (2D) interfaces individually. Here, we demonstrate the electro-intercalation of lithium at the level of individual atomic interfaces of dissimilar vdW layers. Electrochemical devices based on vdW heterostructures comprised of deterministically stacked hexagonal boron nitride, graphene (G) and molybdenum dichalcogenide (MoCh2; Ch = S, Se) layers are fabricated, enabling the direct resolution of intermediate stages in the intercalation of discrete heterointerfaces and the extent of charge transfer to individual layers. Operando magnetoresistance and optical spectroscopy coupled with low-temperature quantum magneto-oscillation measurements show that the creation of intimate vdW heterointerfaces between G and MoCh2 engenders over 10-fold accumulation of charge in MoCh2 compared to MoCh2/MoCh2 homointerfaces, while enforcing a ca. 0.5 V more negative intercalation potential than that of bulk MoCh2. Beyond energy storage, our new experimental methodology to manipulate and characterize the electrochemical behavior of layered systems opens up novel approaches to controlling the charge density in 2D (opto)electronic devices.

 

Title:
Strong coupling Bose polarons out of equilibrium: Dynamical RG approach
Authors:
Grusdt, Fabian; Seetharam, Kushal; Shchadilova, Yulia; Demler, Eugene
Publication:
eprint arXiv:1711.03478
Publication Date:
11/2017
Origin:
ARXIV
Keywords:
Condensed Matter - Quantum Gases, Condensed Matter - Other Condensed Matter, Quantum Physics
Comment:
19 pages, 7 figures, 2 appendices
Bibliographic Code:
2017arXiv171103478G

Abstract

When a mobile impurity interacts with a surrounding bath of bosons, it forms a polaron. Numerous methods have been developed to calculate how the energy and the effective mass of the polaron are renormalized by the medium for equilibrium situations. Here we address the much less studied non-equilibrium regime and investigate how polarons form dynamically in time. To this end, we develop a time-dependent renormalization group approach which allows calculations of all dynamical properties of the system and takes into account the effects of quantum fluctuations in the polaron cloud. We apply this method to calculate trajectories of polarons following a sudden quench of the impurity-boson interaction strength, revealing how the polaronic cloud around the impurity forms in time. Such trajectories provide additional information about the polaron's properties which are challenging to extract directly from the spectral function measured experimentally using ultracold atoms. At strong couplings, our calculations predict the appearance of trajectories where the impurity wavers back at intermediate times as a result of quantum fluctuations. Our method is applicable to a broader class of non-equilibrium problems. We also apply it to calculate the spectral function and find good agreement with experimental results. At very strong couplings, we predict that quantum fluctuations lead to the appearance of a dark continuum with strongly suppressed spectral weight at low energies. While our calculations start from an effective Fr\"ohlich Hamiltonian describing impurities in a three-dimensional Bose-Einstein condensate, we also calculate the effects of additional terms in the Hamiltonian beyond the Fr\"ohlich paradigm. We demonstrate that the main effect of these additional terms on the attractive side of a Feshbach resonance is to renormalize the coupling strength of the effective Fr\"ohlich model.

 

Title:
Selective excitation and imaging of ultraslow phonon polaritons in thin hexagonal boron nitride crystals
Authors:
Ambrosio, Antonio; Tamagnone, Michele; Chaudhary, Kundan; Jauregui, Luis A.; Kim, Philip; Wilson, William L.; Capasso, Federico
Publication:
eprint arXiv:1711.04324
Publication Date:
11/2017
Origin:
ARXIV
Keywords:
Physics - Applied Physics
Bibliographic Code:
2017arXiv171104324A

Abstract

Polaritons in 2D and van der Waals (vdW) materials have been investigated in several recent works as an innovative platform for light-matter interaction, rich of new physical phenomena.Hexagonal Boron Nitride (h-BN), in particular, is an out of plane anisotropic material (while it is in-plane isotropic) with two very strong phonon polaritons bands where the permittivity becomes negative. In the first restrahlen band (RS1, 780-830 cm-1) the relative out of plane permittivity is negative, while in the second restrahlen band (RS2, 1370-1610 cm-1) the relative in-plane permittivity is negative. Due to these optical properties, thin h-BN flakes support guided modes which have been observed experimentally both via far field and near field methods. In this work, we show how selectively excite the more confined modes in the RS1 and RS2 bands. The supported guided modes have phase and group velocities respectively tens and hundreds of times slower than the speed of light. We also show the possibility of full hyperspectral nano-imaging of modes in RS1 band by means of photo-induced force microscopy (PiFM). Moreover, a direct comparison of (PiFM) and scattering-type near-field microscopy (s-SNOM) is obtained by imaging the modes of the RS2 band with both techniques implemented on the same platform. The possibility of addressing ultraslow (ultraconfined) polaritonic modes of h-BN crystal flakes together with the possibility of optical nano-imaging in both the restrahlen bands have many innovative aspects that can lead to unprecedented schemes for strong light-matter interaction, slow and confined light.

 

Title:
Demonstration of Single Barium Ion Sensitivity for Neutrinoless Double Beta Decay using Single Molecule Fluorescence Imaging
Authors:
McDonald, A. D.; Jones, B. J. P.; Nygren, D. R.;... Guenette, R.;... ; and 70 coauthors
Publication:
eprint arXiv:1711.04782
Publication Date:
11/2017
Origin:
ARXIV
Keywords:
Physics - Instrumentation and Detectors, High Energy Physics - Experiment, Nuclear Experiment
Comment:
Submitted to PRL
Bibliographic Code:
2017arXiv171104782M

Abstract

A new method to tag the barium daughter in the double beta decay of $^{136}$Xe is reported. Using the technique of single molecule fluorescent imaging (SMFI), individual barium dication (Ba$^{++}$) resolution at a transparent scanning surface has been demonstrated. A single-step photo-bleach confirms the single ion interpretation. Individual ions are localized with super-resolution ($\sim$2~nm), and detected with a statistical significance of 12.9~$\sigma$ over backgrounds. This lays the foundation for a new and potentially background-free neutrinoless double beta decay technology, based on SMFI coupled to high pressure xenon gas time projection chambers.

 

Title:
Multi-Stage Transformation and Lattice Fluctuation at AgCl-Ag Interface
Authors:
Du, Jingshan S.; Park, Jungwon; Kim, QHwan; Jhe, Wonho; Dravid, Vinayak P.; Yang, Deren; Weitz, David A.
Publication:
eprint arXiv:1711.04899
Publication Date:
11/2017
Origin:
ARXIV
Keywords:
Physics - Chemical Physics, Condensed Matter - Materials Science
Comment:
21 pages, 5 figures; accepted for publication in J. Phys. Chem. Lett
Bibliographic Code:
2017arXiv171104899D

Abstract

Solid-state transformation is often accompanied by mechanical expansion/compression, due to their volume change and structural evolution at interfaces at the atomic scale. However, these two types of dynamics are usually difficult to monitor in the same time. In this work, we use in-situ transmission electron microscopy to directly study the reduction transformation at the AgCl-Ag interface. Three stages of lattice fluctuations were identified and correlated to the structural evolution. During the steady state, a quasi-layered growth mode of Ag in both vertical and lateral directions were observed due to the confinement of AgCl lattices. The development of planar defects and depletion of AgCl are respectively associated with lattice compression and relaxation. Topography and structure of decomposing AgCl was further monitored by in-situ scanning transmission electron microscopy. Silver species are suggested to originate from both the surface and the interior of AgCl, and be transported to the interface. Such mass transport may have enabled the steady state and lattice compression in this volume-shrinking transformation.

 

Title:
Relaxation to a Phase-locked Equilibrium State in a One-dimensional Bosonic Josephson Junction
Authors:
Pigneur, Marine; Berrada, Tarik; Bonneau, Marie; Schumm, Thorsten; Demler, Eugene; Schmiedmayer, Jörg
Publication:
eprint arXiv:1711.06635
Publication Date:
11/2017
Origin:
ARXIV
Keywords:
Quantum Physics, Condensed Matter - Quantum Gases, Physics - Atomic Physics
Comment:
9 pages, 5 figures
Bibliographic Code:
2017arXiv171106635P

Abstract

We present an experimental study on the non-equilibrium tunnel dynamics of two coupled one-dimensional Bose-Einstein quasi-condensates deep in the Josephson regime. Josephson oscillations are initiated by splitting a single one-dimensional condensate and imprinting a relative phase between the superfluids. Regardless of the initial state and experimental parameters, the dynamics of the relative phase and atom number imbalance shows a relaxation to a phase-locked steady state. The latter is characterized by a high phase coherence and reduced fluctuations with respect to the initial state. We propose an empirical model based on the analogy with the anharmonic oscillator to describe the effect of various experimental parameters. A microscopic theory compatible with our observations is still missing.

 

Title:
Invariant metrics on negatively pinched complete K\"ahler manifolds
Authors:
Wu, Damin; Yau, Shing-Tung
Publication:
eprint arXiv:1711.09475
Publication Date:
11/2017
Origin:
ARXIV
Keywords:
Mathematics - Differential Geometry, Mathematics - Complex Variables
Bibliographic Code:
2017arXiv171109475W

Abstract

We prove that a complete K\"ahler manifold with holomorphic curvature bounded between two negative constants admits a unique complete K\"ahler-Einstein metric. We also show this metric and the Kobayashi-Royden metric are both uniformly equivalent to the background K\"ahler metric. Furthermore, all three metrics are shown to be uniformly equivalent to the Bergman metric, if the complete K\"ahler manifold is simply-connected, with the sectional curvature bounded between two negative constants. In particular, we confirm two conjectures of R. E. Greene and H. Wu posted in 1979.

 

Title:
Developing the 3-Point Correlation Function For the Turbulent Interstellar Medium
Authors:
Portillo, Stephen K. N.; Slepian, Zachary; Burkhart, Blakesley; Kahraman, Sule; Finkbeiner, Douglas P.
Publication:
eprint arXiv:1711.09907
Publication Date:
11/2017
Origin:
ARXIV
Keywords:
Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - Astrophysics of Galaxies
Comment:
15 pages, 14 figures
Bibliographic Code:
2017arXiv171109907P

Abstract

We present the first application of the angle-dependent 3-Point Correlation Function (3PCF) to the density fields magnetohydrodynamic (MHD) turbulence simulations intended to model interstellar (ISM) turbulence. Previous work has demonstrated that the angle-averaged bispectrum, the 3PCF's Fourier-space analog, is sensitive to the sonic and Alfv\'enic Mach numbers of turbulence. Here we show that introducing angular information via multipole moments with respect to the triangle opening angle offers considerable additional discriminatory power on these parameters. We exploit a fast, order $N_{\rm g} \log N_{\rm g}$ ($N_{\rm g}$ the number of grid cells used for a Fourier Transform) 3PCF algorithm to study a suite of MHD turbulence simulations with 10 different combinations of sonic and Alfv\'enic Mach numbers over a range from sub to super-sonic and sub to super-Alfv\'{e}nic. The 3PCF algorithm's speed for the first time enables full quantification of the time-variation of our signal: we study 9 timeslices for each condition, demonstrating that the 3PCF is sufficiently time-stable to be used as an ISM diagnostic. In future, applying this framework to 3-D dust maps will enable better treatment of dust as a cosmological foreground as well as reveal conditions in the ISM that shape star formation.

 

Title:
Topological order in the pseudogap metal
Authors:
Scheurer, Mathias S.; Chatterjee, Shubhayu; Wu, Wei; Ferrero, Michel; Georges, Antoine; Sachdev, Subir
Publication:
eprint arXiv:1711.09925
Publication Date:
11/2017
Origin:
ARXIV
Keywords:
Condensed Matter - Strongly Correlated Electrons, High Energy Physics - Theory
Comment:
8+15 pages, 10 figures
Bibliographic Code:
2017arXiv171109925S

Abstract

We compute the electronic Green's function of the topologically ordered Higgs phase of a SU(2) gauge theory of fluctuating antiferromagnetism on the square lattice. The results are compared with cluster extensions of dynamical mean field theory, and quantum Monte Carlo calculations, on the pseudogap phase of the strongly interacting hole-doped Hubbard model. Good agreement is found in the momentum, frequency, hopping, and doping dependencies of the spectral function and electronic self-energy. We show that lines of (approximate) zeros of the zero-frequency electronic Green's function are signs of the underlying topological order of the gauge theory, and describe how these lines of zeros appear in our theory of the Hubbard model. We also derive a modified, non-perturbative version of the Luttinger theorem that holds in the Higgs phase.

 

Title:
Logarithmic singularities and quantum oscillations in magnetically doped topological insulators
Authors:
Nandi, Debaleena; Sodemann, Inti; Shain, Kevin; Lee, Gil-Ho; Huang, Ko-Fan; Chang, Cui-Zu; Ou, Yunbo; Lee, Shu-Ping; Ward, Jonathan; Moodera, Jagadeesh S.; Kim, Philip; Yacoby, Amir
Publication:
eprint arXiv:1711.10675
Publication Date:
11/2017
Origin:
ARXIV
Keywords:
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Mesoscale and Nanoscale Physics
Comment:
9 pages, 10 figures
Bibliographic Code:
2017arXiv171110675N

Abstract

We report magnetotransport measurements on magnetically doped (Bi,Sb)$_2$Te$_3$ films grown by molecular beam epitaxy. In Hallbar devices, logarithmic dependence on temperature and bias voltage are obseved in both the longitudinal and anomalous Hall resistance. The interplay of disorder and electron-electron interactions is found to explain quantitatively the observed logarithmic singularities and is a dominant scattering mechanism in these samples. Submicron scale devices exhibit intriguing quantum oscillations at high magnetic fields with dependence on bias voltage. The observed quantum oscillations can be attributed to bulk and surface transport.

 

Title:
Topological Order from Disorder and the Quantized Hall Thermal Metal: Possible Applications to the $\nu = 5/2$ State
Authors:
Wang, Chong; Vishwanath, Ashvin; Halperin, Bertrand I.
Publication:
eprint arXiv:1711.11557
Publication Date:
11/2017
Origin:
ARXIV
Keywords:
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Mesoscale and Nanoscale Physics
Comment:
12 pages + references, 9 figures
Bibliographic Code:
2017arXiv171111557W

Abstract

Although numerical studies modeling the quantum hall effect at filling fraction $5/2$ predict either the Pfaffian (Pf) or its particle hole conjugate, the anti-Pfaffian (aPf) state, recent experiments appear to favor a quantized thermal hall conductivity with quantum number $K=5/2$ , rather than the value $K=7/2$ or $K=3/2$ expected for the Pf or aPF state, respectively. While a particle hole symmetric topological order (the PH-Pfaffian) would be consistent with the experiments, this state is believed to be energetically unfavorable in a homogenous system. Here we study the effects of disorder that are assumed to locally nucleate domains of Pf and aPf. When the disorder is relatively weak and the size of domains is relatively large, we find that when the electrical Hall conductance is on the quantized plateau with $\sigma_{xy} = (5/2)(e^2/h)$, the value of $K$ can be only 7/2 or 3/2, with a possible first-order-like transition between them as the magnetic field is varied. However, for sufficiently strong disorder an intermediate state might appear, which we analyze within a network model of the domain walls. Predominantly, we find a thermal metal phase, where $K$ varies continuously and the longitudinal thermal conductivity is non-zero, while the electrical Hall conductivity remains quantized at $(5/2)e^2/h$. However, in a restricted parameter range we find a thermal insulator with $K=5/2$, a disorder stabilized phase which is adiabatically connected to the PH-Pfaffian. We discuss a possible scenario to rationalize these special values of parameters.

 

Title:
Symmetry indicators and anomalous surface states of topological crystalline insulators
Authors:
Khalaf, Eslam; Po, Hoi Chun; Vishwanath, Ashvin; Watanabe, Haruki
Publication:
eprint arXiv:1711.11589
Publication Date:
11/2017
Origin:
ARXIV
Keywords:
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science, High Energy Physics - Theory
Comment:
22 pages; 10 figures & 4 tables
Bibliographic Code:
2017arXiv171111589K

Abstract

The rich variety of crystalline symmetries in solids leads to a plethora of topological crystalline insulators (TCIs) featuring distinct physical properties, which are conventionally understood in terms of bulk invariants specialized to the symmetries at hand. While isolated examples of TCI have been identified and studied, the same variety demands a unified theoretical framework. In this work, we show how the surfaces of TCIs can be analyzed within a general surface theory with multiple flavors of Dirac fermions, whose mass terms transform in specific ways under crystalline symmetries. We identify global obstructions to achieving a fully gapped surface, which typically lead to gapless domain walls on suitably chosen surface geometries. We perform this analysis for all 32 point groups, and subsequently for all 230 space groups, for spin-orbit-coupled electrons. We recover all previously discussed TCIs in this symmetry class, including those with "hinge" surface states. Finally, we make connections to the bulk band topology as diagnosed through symmetry-based indicators. We show that spin-orbit-coupled band insulators with nontrivial symmetry indicators are always accompanied by surface states that must be gapless somewhere on suitably chosen surfaces. We provide an explicit mapping between symmetry indicators, which can be readily calculated, and the characteristic surface states of the resulting TCIs.

 

Title:
Evaluating Small Sphere Limit of the Wang-Yau Quasi-Local Energy
Authors:
Chen, Po-Ning; Wang, Mu-Tao; Yau, Shing-Tung
Publication:
Communications in Mathematical Physics, Online First
Publication Date:
11/2017
Origin:
SPRINGER
Abstract Copyright:
(c) 2017: Springer-Verlag GmbH Germany, part of Springer Nature
DOI:
10.1007/s00220-017-3033-4
Bibliographic Code:
2017CMaPh.tmp..380C

Abstract

In this article, we study the small sphere limit of the Wang-Yau quasi-local energy defined in Wang and Yau (Phys Rev Lett 102(2):021101, 2009, Commun Math Phys 288(3):919-942, 2009). Given a point p in a spacetime N, we consider a canonical family of surfaces approaching p along its future null cone and evaluate the limit of the Wang-Yau quasi-local energy. The evaluation relies on solving an "optimal embedding equation" whose solutions represent critical points of the quasi-local energy. For a spacetime with matter fields, the scenario is similar to that of the large sphere limit found in Chen et al. (Commun Math Phys 308(3):845-863, 2011). Namely, there is a natural solution which is a local minimum, and the limit of its quasi-local energy recovers the stress-energy tensor at p. For a vacuum spacetime, the quasi-local energy vanishes to higher order and the solution of the optimal embedding equation is more complicated. Nevertheless, we are able to show that there exists a solution that is a local minimum and that the limit of its quasi-local energy is related to the Bel-Robinson tensor. Together with earlier work (Chen et al. 2011), this completes the consistency verification of the Wang-Yau quasi-local energy with all classical limits.

 

Title:
Measurement of detector-corrected observables sensitive to the anomalous production of events with jets and large missing transverse momentum in \varvec{pp} collisions at √{s}=13 TeV using the ATLAS detector
Authors:
Aaboud, M.; Aad, G.; Abbott, B.; Abdallah, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2861 coauthors
Publication:
The European Physical Journal C, Volume 77, Issue 11, article id. #765, 31 pp. (EPJC Homepage)
Publication Date:
11/2017
Origin:
SPRINGER
Abstract Copyright:
(c) 2017: CERN for the benefit of the ATLAS collaboration
DOI:
10.1140/epjc/s10052-017-5315-6
Bibliographic Code:
2017EPJC...77..765A

Abstract

Observables sensitive to the anomalous production of events containing hadronic jets and missing momentum in the plane transverse to the proton beams at the Large Hadron Collider are presented. The observables are defined as a ratio of cross sections, for events containing jets and large missing transverse momentum to events containing jets and a pair of charged leptons from the decay of a Z/γ ^* boson. This definition minimises experimental and theoretical systematic uncertainties in the measurements. This ratio is measured differentially with respect to a number of kinematic properties of the hadronic system in two phase-space regions; one inclusive single-jet region and one region sensitive to vector-boson-fusion topologies. The data are found to be in agreement with the Standard Model predictions and used to constrain a variety of theoretical models for dark-matter production, including simplified models, effective field theory models, and invisible decays of the Higgs boson. The measurements use 3.2 fb^{-1} of proton-proton collision data recorded by the ATLAS experiment at a centre-of-mass energy of 13 {TeV} and are fully corrected for detector effects, meaning that the data can be used to constrain new-physics models beyond those shown in this paper.

 

Title:
Superconformal index, BPS monodromy and chiral algebras
Authors:
Cecotti, Sergio; Song, Jaewon; Vafa, Cumrun; Yan, Wenbin
Publication:
Journal of High Energy Physics, Volume 2017, Issue 11, article id. #13, 90 pp.
Publication Date:
11/2017
Origin:
SPRINGER
Keywords:
Conformal Field Theory, Supersymmetric Gauge Theory
Abstract Copyright:
(c) 2017: The Author(s)
DOI:
10.1007/JHEP11(2017)013
Bibliographic Code:
2017JHEP...11..013C

Abstract

We show that specializations of the 4d N=2 superconformal index labeled by an integer N is given by Tr ℳ N where ℳ is the Kontsevich-Soibelman monodromy operator for BPS states on the Coulomb branch. We provide evidence that the states enumerated by these limits of the index lead to a family of 2d chiral algebras A_N. This generalizes the recent results for the N = -1 case which corresponds to the Schur limit of the superconformal index. We show that this specialization of the index leads to the same integrand as that of the elliptic genus of compactification of the superconformal theory on S2 × T2 where we turn on 1/2N units of U(1)r flux on S2.

 

Title:
Measurement of b-hadron pair production with the ATLAS detector in proton-proton collisions at √{s}=8 TeV
Authors:
Aaboud, M.; Aad, G.; Abbott, B.; Abdallah, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2856 coauthors
Publication:
Journal of High Energy Physics, Volume 2017, Issue 11, article id. #62, 51 pp.
Publication Date:
11/2017
Origin:
SPRINGER
Keywords:
B physics, Hadron-Hadron scattering (experiments)
Abstract Copyright:
(c) 2017: The Author(s)
DOI:
10.1007/JHEP11(2017)062
Bibliographic Code:
2017JHEP...11..062A

Abstract

A measurement of b-hadron pair production is presented, based on a data set corresponding to an integrated luminosity of 11.4 fb-1 of proton-proton collisions recorded at √{s}=8 TeV with the ATLAS detector at the LHC. Events are selected in which a b-hadron is reconstructed in a decay channel containing J/ψ → μμ, and a second b-hadron is reconstructed in a decay channel containing a muon. Results are presented in a fiducial volume defined by kinematic requirements on three muons based on those used in the analysis. The fiducial cross section is measured to be 17.7 ± 0.1(stat.) ± 2.0(syst.) nb. A number of normalised differential cross sections are also measured, and compared to predictions from the P ythia8, H erwig++, M adG raph5_ aMC@NLO+P ythia8 and S herpa event generators, providing new constraints on heavy flavour production. [Figure not available: see fulltext.]

 

Title:
Measurement of the t\overline{t}γ production cross section in proton-proton collisions at √{s}=8 TeV with the ATLAS detector
Authors:
Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2869 coauthors
Publication:
Journal of High Energy Physics, Volume 2017, Issue 11, article id. #86, 43 pp.
Publication Date:
11/2017
Origin:
SPRINGER
Keywords:
Hadron-Hadron scattering (experiments), Top physics
Abstract Copyright:
(c) 2017: The Author(s)
DOI:
10.1007/JHEP11(2017)086
Bibliographic Code:
2017JHEP...11..086A

Abstract

The cross section of a top-quark pair produced in association with a photon is measured in proton-proton collisions at a centre-of-mass energy of √{s}=8 TeV with 20.2 fb-1 of data collected by the ATLAS detector at the Large Hadron Collider in 2012. The measurement is performed by selecting events that contain a photon with transverse momentum p T > 15 GeV, an isolated lepton with large transverse momentum, large missing transverse momentum, and at least four jets, where at least one is identified as originating from a b-quark. The production cross section is measured in a fiducial region close to the selection requirements. It is found to be 139 ± 7 (stat.) ± 17 (syst.) fb, in good agreement with the theoretical prediction at next-to-leading order of 151 ± 24 fb. In addition, differential cross sections in the fiducial region are measured as a function of the transverse momentum and pseudorapidity of the photon. [Figure not available: see fulltext.]

 

Title:
Complex Chern-Simons from M5-branes on the squashed three-sphere
Authors:
Córdova, Clay; Jafferis, Daniel L.
Publication:
Journal of High Energy Physics, Volume 2017, Issue 11, article id. #119, 30 pp.
Publication Date:
11/2017
Origin:
SPRINGER
Keywords:
Effective Field Theories, Field Theories in Higher Dimensions, Supersymmetric Gauge Theory, Topological Field Theories
Abstract Copyright:
(c) 2017: The Author(s)
DOI:
10.1007/JHEP11(2017)119
Bibliographic Code:
2017JHEP...11..119C

Abstract

We derive an equivalence between the (2,0) superconformal M5-brane field theory dimensionally reduced on a squashed three-sphere, and Chern-Simons theory with complex gauge group. In the reduction, the massless fermions obtain an action which is second order in derivatives and are reinterpreted as ghosts for gauge fixing the emergent non-compact gauge symmetry. A squashing parameter in the geometry controls the imaginary part of the complex Chern-Simons level.

 

Title:
Plasmon Reflections by Topological Electronic Boundaries in Bilayer Graphene
Authors:
Jiang, Bor-Yuan; Ni, Guang-Xin; Addison, Zachariah; Shi, Jing K.; Liu, Xiaomeng; Zhao, Shu Yang Frank; Kim, Philip; Mele, Eugene J.; Basov, Dimitri N.; Fogler, Michael M.
Affiliation:
AA(0000-0003-4242-3987)
Publication:
Nano Letters, vol. 17, issue 11, pp. 7080-7085
Publication Date:
11/2017
Origin:
CROSSREF
DOI:
10.1021/acs.nanolett.7b03816
Bibliographic Code:
2017NanoL..17.7080J

Abstract

Domain walls separating regions of AB and BA interlayer stacking in bilayer graphene have attracted attention as novel examples of structural solitons, topological electronic boundaries, and nanoscale plasmonic scatterers. We show that strong coupling of domain walls to surface plasmons observed in infrared nanoimaging experiments is due to topological chiral modes confined to the walls. The optical transitions among these chiral modes and the band continua enhance the local ac conductivity, which leads to plasmon reflection by the domain walls. The imaging reveals two kinds of plasmonic standing-wave interference patterns, which we attribute to shear and tensile domain walls. We compute the electronic structure of both wall varieties and show that the tensile wall contain additional confined bands which produce a structure-specific contrast of the local conductivity. The calculated plasmonic interference profiles are in quantitative agreement with our experiments.

 

Title:
Measurement of jet pT correlations in Pb + Pb and pp collisions at √{sNN} = 2.76 TeV with the ATLAS detector
Authors:
Aaboud, M.; Aad, G.; Abbott, B.; Abdallah, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2825 coauthors
Publication:
Physics Letters B, Volume 774, p. 379-402.
Publication Date:
11/2017
Origin:
ELSEVIER
Abstract Copyright:
(c) 2017 Elsevier Science B.V. All rights reserved.
DOI:
10.1016/j.physletb.2017.09.078
Bibliographic Code:
2017PhLB..774..379A

Abstract

Measurements of dijet pT correlations in Pb +Pb and pp collisions at a nucleon-nucleon centre-of-mass energy of √{sNN} = 2.76 TeV are presented. The measurements are performed with the ATLAS detector at the Large Hadron Collider using Pb+Pb and pp data samples corresponding to integrated luminosities of 0.14 nb-1 and 4.0 pb-1, respectively. Jets are reconstructed using the anti-kt algorithm with radius parameter values R = 0.3 and R = 0.4. A background subtraction procedure is applied to correct the jets for the large underlying event present in Pb +Pb collisions. The leading and sub-leading jet transverse momenta are denoted pT1 and pT2. An unfolding procedure is applied to the two-dimensional (pT1, pT2) distributions to account for experimental effects in the measurement of both jets. Distributions of (1 / N) dN / dxJ, where xJ=pT2/pT1, are presented as a function of pT1 and collision centrality. The distributions are found to be similar in peripheral Pb +Pb collisions and pp collisions, but highly modified in central Pb +Pb collisions. Similar features are present in both the R = 0.3 and R = 0.4 results, indicating that the effects of the underlying event are properly accounted for in the measurement. The results are qualitatively consistent with expectations from partonic energy loss models.

 

Title:
Search for heavy resonances decaying to a W or Z boson and a Higgs boson in the qq bar (‧) b b bar final state in pp collisions at √{ s } = 13 TeV with the ATLAS detector
Authors:
Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2869 coauthors
Publication:
Physics Letters B, Volume 774, p. 494-515.
Publication Date:
11/2017
Origin:
ELSEVIER
Abstract Copyright:
(c) 2017 Elsevier Science B.V. All rights reserved.
DOI:
10.1016/j.physletb.2017.09.066
Bibliographic Code:
2017PhLB..774..494A

Abstract

A search for heavy resonances decaying to a W or Z boson and a Higgs boson in the qq bar(‧) b b bar final state is described. The search uses 36.1 fb-1 of proton-proton collision data at √{ s } = 13 TeV collected by the ATLAS detector at the CERN Large Hadron Collider in 2015 and 2016. The data are in agreement with the Standard Model expectations, with the largest excess found at a resonance mass of 3.0 TeV with a local (global) significance of 3.3 (2.1) σ. The results are presented in terms of constraints on a simplified model with a heavy vector triplet. Upper limits are set on the production cross-section times branching ratio for resonances decaying to a W (Z) boson and a Higgs boson, itself decaying to b b bar , in the mass range between 1.1 and 3.8 TeV at 95% confidence level; the limits range between 83 and 1.6 fb (77 and 1.1 fb) at 95% confidence level.

 

Title:
Dynamics of quantum information in many-body localized systems
Authors:
Bañuls, M. C.; Yao, N. Y.; Choi, S.; Lukin, M. D.; Cirac, J. I.
Publication:
Physical Review B, Volume 96, Issue 17, id.174201 (PhRvB Homepage)
Publication Date:
11/2017
Origin:
APS
Abstract Copyright:
2017: American Physical Society
DOI:
10.1103/PhysRevB.96.174201
Bibliographic Code:
2017PhRvB..96q4201B

Abstract

We characterize the information dynamics of strongly disordered systems using a combination of analytics, exact diagonalization, and matrix product operator (MPO) simulations. More specifically, we study the spreading of quantum information in three different scenarios: thermalizing, Anderson localized, and many-body localized. We qualitatively distinguish these cases by quantifying the amount of remnant information in a local region. The nature of the dynamics is further explored by computing the propagation of mutual information with respect to varying partitions. Finally, we demonstrate that classical simulability, as captured by the magnitude of MPO truncation errors, exhibits enhanced fluctuations near the localization transition, suggesting the possibility of its use as a diagnostic of the critical point.

 

Title:
Realizing and adiabatically preparing bosonic integer and fractional quantum Hall states in optical lattices
Authors:
He, Yin-Chen; Grusdt, Fabian; Kaufman, Adam; Greiner, Markus; Vishwanath, Ashvin
Publication:
Physical Review B, Volume 96, Issue 20, id.201103 (PhRvB Homepage)
Publication Date:
11/2017
Origin:
APS
Abstract Copyright:
2017: American Physical Society
DOI:
10.1103/PhysRevB.96.201103
Bibliographic Code:
2017PhRvB..96t1103H

Abstract

We study the ground states of two-dimensional lattice bosons in an artificial gauge field. Using state-of-the-art density matrix renormalization group (DMRG) simulations we obtain the zero-temperature phase diagram for hard-core bosons at densities nb with flux nϕ per unit cell, which determines a filling ν =nb/nϕ . We find the bosonic Jain sequence [ν =p /(p +1 )] states, in particular, a bosonic integer quantum Hall phase at ν =2 , are fairly robust in the hard-core boson limit, In addition to identifying Hamiltonians whose ground states realize these phases, we discuss their preparation, beginning from independent chains, and ramping up interchain couplings. Using time-dependent DMRG simulations, these are shown to reliably produce states close to the ground state for experimentally relevant system sizes. Our proposal only utilizes existing experimental capabilities.

 

Title:
BICEP2 / Keck Array IX: New bounds on anisotropies of CMB polarization rotation and implications for axionlike particles and primordial magnetic fields
Authors:
BICEP2 Collaboration; Keck Array Collaboration; Ade, P. A. R.; Ahmed, Z.; Aikin, R. W.;... Dvorkin, C.;... Kovac, J. M.;... and 60 coauthors.
Publication:
Physical Review D, Volume 96, Issue 10, id.102003 (PhRvD Homepage)
Publication Date:
11/2017
Origin:
APS
Abstract Copyright:
2017: American Physical Society
DOI:
10.1103/PhysRevD.96.102003
Bibliographic Code:
2017PhRvD..96j2003B

Abstract

We present the strongest constraints to date on anisotropies of cosmic microwave background (CMB) polarization rotation derived from 150 GHz data taken by the BICEP2 & Keck Array CMB experiments up to and including the 2014 observing season (BK14). The definition of the polarization angle in BK14 maps has gone through self-calibration in which the overall angle is adjusted to minimize the observed T B and E B power spectra. After this procedure, the Q U maps lose sensitivity to a uniform polarization rotation but are still sensitive to anisotropies of polarization rotation. This analysis places constraints on the anisotropies of polarization rotation, which could be generated by CMB photons interacting with axionlike pseudoscalar fields or Faraday rotation induced by primordial magnetic fields. The sensitivity of BK14 maps (˜3 μ K -arc min ) makes it possible to reconstruct anisotropies of the polarization rotation angle and measure their angular power spectrum much more precisely than previous attempts. Our data are found to be consistent with no polarization rotation anisotropies, improving the upper bound on the amplitude of the rotation angle spectrum by roughly an order of magnitude compared to the previous best constraints. Our results lead to an order of magnitude better constraint on the coupling constant of the Chern-Simons electromagnetic term ga γ≤7.2 ×10-2/HI (95% confidence) than the constraint derived from the B -mode spectrum, where HI is the inflationary Hubble scale. This constraint leads to a limit on the decay constant of 10-6≲fa/Mpl at mass range of 10-33≤ma≤10-28 eV for r =0.01 , assuming ga γ˜α /(2 π fa) with α denoting the fine structure constant. The upper bound on the amplitude of the primordial magnetic fields is 30 nG (95% confidence) from the polarization rotation anisotropies.

 

Title:
Thermal diffusivity and chaos in metals without quasiparticles
Authors:
Blake, Mike; Davison, Richard A.; Sachdev, Subir
Publication:
Physical Review D, Volume 96, Issue 10, id.106008 (PhRvD Homepage)
Publication Date:
11/2017
Origin:
APS
Abstract Copyright:
2017: American Physical Society
DOI:
10.1103/PhysRevD.96.106008
Bibliographic Code:
2017PhRvD..96j6008B

Abstract

We study the thermal diffusivity DT in models of metals without quasiparticle excitations ("strange metals"). The many-body quantum chaos and transport properties of such metals can be efficiently described by a holographic representation in a gravitational theory in an emergent curved spacetime with an additional spatial dimension. We find that at generic infrared fixed points DT is always related to parameters characterizing many-body quantum chaos: the butterfly velocity vB and Lyapunov time τL through DT˜vB2τL. The relationship holds independently of the charge density, periodic potential strength, or magnetic field at the fixed point. The generality of this result follows from the observation that the thermal conductivity of strange metals depends only on the metric near the horizon of a black hole in the emergent spacetime and is otherwise insensitive to the profile of any matter fields.

 

Title:
Active elastohydrodynamics of vesicles in narrow blind constrictions
Authors:
Fai, T. G.; Kusters, R.; Harting, J.; Rycroft, C. H.; Mahadevan, L.
Publication:
Physical Review Fluids, Volume 2, Issue 11, id.113601
Publication Date:
11/2017
Origin:
APS
Abstract Copyright:
2017: American Physical Society
DOI:
10.1103/PhysRevFluids.2.113601
Bibliographic Code:
2017PhRvF...2k3601F

Abstract

Fluid-resistance limited transport of vesicles through narrow constrictions is a recurring theme in many biological and engineering applications. Inspired by the motor-driven movement of soft membrane-bound vesicles into closed neuronal dendritic spines, here we study this problem using a combination of passive three-dimensional simulations and a simplified semianalytical theory for the active transport of vesicles forced through constrictions by molecular motors. We show that the motion of these objects is characterized by two dimensionless quantities related to the geometry and to the strength of forcing relative to the vesicle elasticity. We use numerical simulations to characterize the transit time for a vesicle forced by fluid pressure through a constriction in a channel and find that relative to an open channel, transport into a blind end leads to the formation of a smaller forward-flowing lubrication layer that strongly impedes motion. When the fluid pressure forcing is complemented by forces due to molecular motors that are responsible for vesicle trafficking into dendritic spines, we find that the competition between motor forcing and fluid drag results in multistable dynamics reminiscent of the real system. Our study highlights the role of nonlocal hydrodynamic effects in determining the kinetics of vesicular transport in constricted geometries.

 

Title:
Search for Dark Matter Produced in Association with a Higgs Boson Decaying to b b ¯ Using 36 fb-1 of p p Collisions at √{s }=13 TeV with the ATLAS Detector
Authors:
Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2874 coauthors
Publication:
Physical Review Letters, Volume 119, Issue 18, id.181804 (PhRvL Homepage)
Publication Date:
11/2017
Origin:
APS
Abstract Copyright:
2017: CERN
DOI:
10.1103/PhysRevLett.119.181804
Bibliographic Code:
2017PhRvL.119r1804A

Abstract

Several extensions of the standard model predict associated production of dark-matter particles with a Higgs boson. Such processes are searched for in final states with missing transverse momentum and a Higgs boson decaying to a b b ¯ pair with the ATLAS detector using 36.1 fb-1 of p p collisions at a center-of-mass energy of 13 TeV at the LHC. The observed data are in agreement with the standard model predictions and limits are placed on the associated production of dark-matter particles and a Higgs boson.

 

Title:
Dynamical Engineering of Interactions in Qudit Ensembles
Authors:
Choi, Soonwon; Yao, Norman Y.; Lukin, Mikhail D.
Publication:
Physical Review Letters, Volume 119, Issue 18, id.183603 (PhRvL Homepage)
Publication Date:
11/2017
Origin:
APS
Abstract Copyright:
2017: American Physical Society
DOI:
10.1103/PhysRevLett.119.183603
Bibliographic Code:
2017PhRvL.119r3603C

Abstract

We propose and analyze a method to engineer effective interactions in an ensemble of d -level systems (qudits) driven by global control fields. In particular, we present (i) a necessary and sufficient condition under which a given interaction can be decoupled, (ii) the existence of a universal sequence that decouples any (cancelable) interaction, and (iii) an efficient algorithm to engineer a target Hamiltonian from an initial Hamiltonian (if possible). We illustrate the potential of this method with two examples. Specifically, we present a 6-pulse sequence that decouples effective spin-1 dipolar interactions and demonstrate that a spin-1 Ising chain can be engineered to study transitions among three distinct symmetry protected topological phases. Our work enables new approaches for the realization of both many-body quantum memories and programmable analog quantum simulators using existing experimental platforms.

 

Title:
Search for Heavy Higgs Bosons A /H Decaying to a Top Quark Pair in p p Collisions at √{s }=8 TeV with the ATLAS Detector
Authors:
Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2872 coauthors
Publication:
Physical Review Letters, Volume 119, Issue 19, id.191803 (PhRvL Homepage)
Publication Date:
11/2017
Origin:
APS
Abstract Copyright:
2017: CERN
DOI:
10.1103/PhysRevLett.119.191803
Bibliographic Code:
2017PhRvL.119s1803A

Abstract

A search for heavy pseudoscalar (A ) and scalar (H ) Higgs bosons decaying into a top quark pair (t t ¯) has been performed with 20.3 fb-1 of proton-proton collision data collected by the ATLAS experiment at the Large Hadron Collider at a center-of-mass energy √{s }=8 TeV . Interference effects between the signal process and standard model t t ¯ production, which are expected to distort the signal shape from a single peak to a peak-dip structure, are taken into account. No significant deviation from the standard model prediction is observed in the t t ¯ invariant mass spectrum in final states with an electron or muon, large missing transverse momentum, and at least four jets. The results are interpreted within the context of a type-II two-Higgs-doublet model. Exclusion limits on the signal strength are derived as a function of the mass mA /H and the ratio of the vacuum expectation values of the two Higgs fields, tan β , for mA /H >500 GeV.

 

Title:
Optimal Design of Experiments by Combining Coarse and Fine Measurements
Authors:
Lee, Alpha A.; Brenner, Michael P.; Colwell, Lucy J.
Publication:
Physical Review Letters, Volume 119, Issue 20, id.208101 (PhRvL Homepage)
Publication Date:
11/2017
Origin:
APS
Abstract Copyright:
2017: American Physical Society
DOI:
10.1103/PhysRevLett.119.208101
Bibliographic Code:
2017PhRvL.119t8101L

Abstract

In many contexts, it is extremely costly to perform enough high-quality experimental measurements to accurately parametrize a predictive quantitative model. However, it is often much easier to carry out large numbers of experiments that indicate whether each sample is above or below a given threshold. Can many such categorical or "coarse" measurements be combined with a much smaller number of high-resolution or "fine" measurements to yield accurate models? Here, we demonstrate an intuitive strategy, inspired by statistical physics, wherein the coarse measurements are used to identify the salient features of the data, while the fine measurements determine the relative importance of these features. A linear model is inferred from the fine measurements, augmented by a quadratic term that captures the correlation structure of the coarse data. We illustrate our strategy by considering the problems of predicting the antimalarial potency and aqueous solubility of small organic molecules from their 2D molecular structure.

 

Title:
Diamond-Based Magnetic Imaging with Fourier Optical Processing
Authors:
Backlund, Mikael P.; Kehayias, Pauli; Walsworth, Ronald L.
Publication:
Physical Review Applied, Volume 8, Issue 5, id.054003
Publication Date:
11/2017
Origin:
APS
Abstract Copyright:
2017: American Physical Society
DOI:
10.1103/PhysRevApplied.8.054003
Bibliographic Code:
2017PhRvP...8e4003B

Abstract

Diamond-based magnetic field sensors have attracted great interest in recent years. In particular, wide-field magnetic imaging using nitrogen-vacancy (NV) centers in diamond has been previously demonstrated in condensed matter, biological, and paleomagnetic applications. Vector magnetic imaging with NV ensembles typically requires a significant applied field (>10 G ) to resolve the contributions from four crystallographic orientations, hindering studies of magnetic samples that require measurement in low or independently specified bias fields. Here we model and measure the complex amplitude distribution of NV emission at the microscope's Fourier plane and show that by modulating this collected light at the Fourier plane, one can decompose the NV ensemble magnetic resonance spectrum into its constituent orientations by purely optical means. This decomposition effectively extends the dynamic range at a given bias field and enables wide-field vector magnetic imaging at arbitrarily low bias fields, thus broadening potential applications of NV imaging and sensing. Our results demonstrate that NV-based microscopy stands to benefit greatly from Fourier optical approaches, which have already found widespread utility in other branches of microscopy.

 

Title:
In celebration of Ilya Lifshitz
Authors:
Grosberg, Alexander Y.; Halperin, Bertrand; Singleton, John
Publication:
Physics Today, vol. 70, issue 11, pp. 44-50
Publication Date:
11/2017
Origin:
CROSSREF
DOI:
10.1063/PT.3.3764
Bibliographic Code:
2017PhT....70k..44G

Abstract

Not Available

 

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