Harvard University Department of Physics

The Morris Loeb Lecture in Physics: Jun Ye

Three lectures by Jun Ye: "Quantum matter and atomic clocks (Oct. 22) "; "Frequency Comb Spectroscopy – from mid-IR to XUV" (Oct. 23); "Cold molecules – a new playground for quantum and chemical physics" (Oct. 24).

New Book by David Morin

This book is a collection of 57 very challenging math problems with detailed solutions. It is written for anyone who enjoys pondering difficult problems for great lengths of time. The problems are mostly classics...

Physical Interpretation of the Partition Function for Colloidal Clusters

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...

UPCOMING EVENTS

Tomorrow

Professor Jun Ye, University of Colorado - Loeb Lecture
Start: 04:15pm - End: 05:15pm
- Quantum matter and atomic clocks
  
  Precise quantum state engineering of individual atoms has led to the unprecedented measurement performance for time and frequency. The use of many atoms enhances the counting statistics, and it also provides new opportunities for understanding and constructing quantum matter to enhance measurement accuracy. At the core of the new JILA three-dimensional optical lattice clock is a quantum gas of fermionic atoms that are spatially correlated to guard against motional and collisional effects. The convolution of precision control of light and matter is helping bridge different disciplines in physics and fostering new capabilities to probe fundamental and emerging phenomena
- 04:15pm
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Tuesday, October 23rd

CMP Special Seminar: Philip Moll (Ecole Polytechnique Federale de Lausanne), hosted by Philip Kim
Start: 01:30pm - End: 03:00pm
- Title: Designing landscapes of correlations and topology: a strain-gradient approach
  
  Abstract: The phase diagrams of strongly correlated materials are typically rich and complex, reflecting the competition of various ordered phases for states at the Fermi level. We currently explore new approaches to fabricate single crystal devices in which multiple of such phases coexist in different locations of a device. A spatial modulation of the correlation strength can be achieved by controlling a strong strain gradient in the sample. Using Focused-Ion-Beam machining, we fabricate micrometer-sized single crystal devices from quantum materials and subject them both to passive strain fields via thermal contraction as well as actively driving them in a MEMS setting. This allows the generation of strong yet well-controlled strain gradients. Two concrete recent examples will be discussed: In the heavy-fermion superconductor CeIrIn5, the hybridization strength of the 4f1-electron with the conduction band can be tuned in real space through strain gradient fields. In the Dirac semi-metal Cd3As2, strain gradients move (and potentially merge) the nodes, leading to the emergence of “pseudo-magnetic” fields which influence the quasiparticles akin to Landau quantization in real magnetic fields. I will present the physical questions that become tangible when strong strain gradients can be controlled, our experimental and technical approaches to generate them, as well as our recent results.
- 01:30pm
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MATH: TBA
Start: 04:00pm - End: 05:00pm
- 04:00pm
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CUA Seminar/Loeb Lecture: Prof. Jun Ye (JILA)
Start: 04:30pm - End: 06:00pm
- 04:30pm
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Wednesday, October 24th

Loeb Lecture - Jun Ye (JILA)
Start: 04:00pm - End: 05:30pm
- 04:00pm
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Prof. Luyi Sun - UCONN
Start: 06:00pm - End: 07:30pm
- 06:00pm
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Thursday, October 25th

CMP Seminar: Vladimir Narovlansky (Weizmann Institute), hosted by Subir Sachdev
Start: 12:00pm - End: 01:00pm
- Title: The renormalization group of quenched disorder
  
  Abstract: A systematic analysis of classical and quantum theories with disorder is performed using renormalization group flow. For the quantum case, this can be done despite the appearance of non-locality in time in the replica theory, leading to several interesting results. The dynamical scaling exponent is shown to be related to a flow of a particular coupling constant, and has a universal form at weak disorder. The renormalization group flow also leads to the identification of new critical exponents for quantum disorder.
- 12:00pm
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ITAMP Lunch Seminar
Start: 12:00pm - End: 01:00pm
- Speaker: Valentin Walther
- 12:00pm
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Friday, October 26th

CMP Special Seminar: Dario Poletti (Singapore University of Technology and Design), hosted by Jamir Marino
Start: 12:00pm - End: 01:00pm
- Title: Current Rectification in Strongly Interacting Open Quantum Systems
  
  Abstract: We study the rectification of spin current in XXZ chains segmented in two parts, each with a different anisotropy parameter. Using exact diagonalization and a matrix product states algorithm we find that a large rectification (of the order of 10^4) is attainable even using a short chain of N=8 spins, when one half of the chain is gapless while the other has large enough anisotropy. We present evidence of diffusive transport when the current is driven in one direction and of a transition to an insulating behavior of the system when driven in the opposite direction, leading to a perfect diode in the thermodynamic limit. The above results are explained in terms of matching of spectrum of magnon excitations between the two halves of the chain. When considering heat baths, we also show a behavior for the heat current with strong similarities to that of the spin current, emphasizing the robustness of the rectification mechanism.
- 12:00pm
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