Physics Home

Condensed Matter/Biophysics Seminars
Fall 2021

Condensed Matter/Biophysics Seminars are in 2205 NPB
Mondays @ 4:05 pm to 4:55 pm

Committee: Yuxuan wang, Xiao-Xiao Zhang and Purushottam Dixit



August 30      

 

Speaker

 

Title

 

Abstract

 

Host

 

September 6 - No seminar (Labor Day holiday)        

 

Speaker

 

Title

 

Abstract

 

Host

 

September 13    

 

Speaker

 

Title

 

Abstract

 

 

Host

 

September 20   

 

Speaker

Dr Sarbajaya Kundu (UF)

 

Title

Competing phases and critical behavior in three coupled spinless Luttinger liquids

 

Abstract

In this talk, I will discuss our recent work involving electronic phase competition in a strongly correlated system of three coupled spinless Luttinger liquids - one of the simplest models where topologically nontrivial chiral orders may be realized. We study the problem as a coupled sine-Gordon model, using a perturbative renormalization group (RG) approach. In contrast with counterparts with fewer fermionic species, here the scaling procedure generates off-diagonal contributions to the phase stiffness matrix, which require both rescaling as well as large rotations of the bosonic fields. These rotations, generally non-abelian in nature, introduce a coupling between different interaction channels even at the tree-level order in the coupling constant scaling equations. We study competing phases in this system, taking into account the aforementioned rotations, and determine its critical behaviour in a variety of interaction parameter regimes where perturbative RG is possible. The phase boundaries are found to be of the Berezinskii-Kosterlitz-Thouless (BKT) type, and we specify the parameter regimes where valley-symmetry breaking, intervalley orders and chiral orders may be observed. Our approach and findings may be relevant for understanding phases and transitions at high magnetic fields in semimetals such as bismuth featuring three Fermi pockets. Ref: arXiv:1906.11053 Authors: Sarbajaya Kundu, Vikram Tripathi

 

Host

Yuxuan Wang

 

September 27   

 

Speaker

Long Ju, MIT

 

Title

Electron Correlation and Electron-Phonon coupling in a Trilayer Graphene/hBN Moire Superlattice

Abstract

When two-dimensional materials with similar lattice constants are stacked vertically, spatial modulation can be induced in the form of moire superlattices. Such superlattices emerged as a novel platform to engineer interlayer interactions between electrons and phonons, which have resulted in correlated and topological electron phenomena. The experimental study of 2D moire superlattices, however, is quite challenging for conventional spectroscopy techniques. In this talk, I will show optical spectroscopy study of a particular moire superlattice that is formed between ABC trilayer graphene and hexagonal boron nitride. I will first show our FTIR photocurrent spectroscopy study of the bandstructure of moire mini-bands, and its implications on the formation of correlated electron ground states. Furthermore, I will show our observation of a strong interlayer electron-phonon coupling that is unique to moire superlattices. These results point to exciting opportunities in engineering and understanding of electronic and optical properties of 2D moire superlattices.

Host

Xiao-Xiao Zhang

 

October 4 

 

Speaker

Lex Kemper, NC State

 

Title

Examining topology and thermodynamics using quantum computers

 

Abstract

Quantum hardware has advanced to the point where it is now possible to perform simulations of physical systems and elucidate their topological and thermodynamic properties, which we will discuss in this talk. I will give a brief introduction to quantum computing and why they might be useful tools for solving problems in condensed matter physics and beyond. Following that, I will present a perspective on thermodynamics of quantum systems ideally suited to quantum computers, namely the zeros of the partition function, or Lee-Yang zeros. We developed quantum circuits to measure the Lee-Yang zeros, and used these to reconstruct the thermodynamic partition function of the XXZ model. The zeros qualitatively show the cross-over from an Ising-like regime to an XY-like regime, making this measurement ideally suitable in a NISQ environment. If time permits, I will discuss our demonstration of how topological properties of physical systems can be measured on quantum computers. We leverage the holonomy of the wavefunctions to obtain a noise-free measurement of the Chern number, which we apply to an interacting fermion model.

 

Host

Peter Hirschfeld

 

October 11 

 

Speaker

Pilar Cossio, Flatiron Institute

 

Title

 

Abstract

 

Host

Purushottam Dixit

 

October 18 

 

Speaker

Jeetain Mittal, Texas A&M

 

Title

Molecular organization in biology: What can computer simulations teach us?

 

Abstract

The formation of membraneless organelles (MLOs) via phase separation of proteins and nucleic acids has emerged as an essential process with which cells can maintain spatiotemporal control. Despite enormous progress in understanding the role of MLOs in biological function in the last ten years or so, the molecular details of the underlying phenomena are only beginning to emerge recently. We use computer simulations of coarse-grained and all-atom models to complement experimental studies to achieve insights into the molecular driving forces underlying biomolecular phase separation. In this talk, I'll highlight results that demonstrate our approach's usefulness for identifying general principles and system-specific insights into biomolecular structure and function. These results also open up new avenues for the design of biomaterials with tunable properties.

Short Bio: Jeetain Mittal is currently a Professor of Chemical Engineering at Texas A&M University. He received his doctorate in Chemical Engineering from the University of Texas, Austin, and worked as a postdoctoral research fellow at the Laboratory of Chemical Physics at the National Institutes of Health. His group is developing predictive physics-based computational tools to identify the fundamental rules that govern structural and compositional ordering in a wide variety of systems with a specific focus on the following active research projects: (1) biomolecular phase separation and (2) nanoparticle superlattice engineering by DNA-mediated interactions.

 

Host

Purushottam Dixit

 

October 25 

 

Speaker

Jia Leo Li, Brown University

 

Title

 

Abstract

 

Host

Xiao-Xiao Zhang

 

November 1 

 

Speaker

Ajit Srivastava, Emory University

 

Title

 

Abstract

 

Host

Xiao-Xiao Zhang

 

November 8 

 

Speaker

Emanuel Tutuc from University of Texas at Austin

 

Title

 

Abstract

 

Host

Dominique Laroche

 

November 15 

 

Speaker

Luiz Santos, Emory University

 

Title

 

Abstract

 

Host

Yuxuan Wang

 

November 22 

 

Speaker

 

Title

 

Abstract

 

Host

 

November 29 

 

Speaker

Yizhuang You, UCSD

 

Title

 

Abstract

 

Host

Yuxuan Wang and Xiao-Xiao Zhang

 

December 6 

 

Speaker

Shenshen Wang, UCLA

 

Title

 

Abstract

 

Host

Purushottam Dixit