Physics Home

Condensed Matter/Biophysics Seminars
Spring 2021

Condensed Matter/Biophysics Seminars are via Zoom until further notiice
on Mondays @ 4:05 pm to 4:55 pm

Contact: Yasu Takano or Dmitrii Maslov



January 11      

 

Speaker

 

Title

 

Abstract

 

Host

 

January 18 (No seminar – MLK Jr Day)      

 

Speaker

NA

 

Title

NA

 

Abstract

NA

 

Host

NA

 

January 25    

 

Speaker

Bo Zhen (Univ. of Pennsylvania)

 

Title

Topological photonics at the nanoscale

 

Abstract

Topological photonics has been of great interest due to both fundamental principles and potential applications. In this talk, I will discuss some of our recent results in linear and nonlinear nanophotonic structures, where topological phenomena are achieved. Their applications in photonics integrated circuits and nonlinear optoelectronic devices will also be discussed. 

 

Host

Xiao-Xiao Zhang

 

February 1   

 

Speaker

Yin-Chen He (Perimeter Institute for Theoretical Physics)

 

Title

Stiefel liquids: from the Dirac spin liquid to a new critical spin liquid

 

Abstract

I will talk about a new type of critical quantum liquids, dubbed Stiefel liquids, that can emerge from the intertwinement of symmetry breaking orders. Our theory is based on 2+1 dimensional nonlinear sigma models on target space SO(N)/SO(4), supplemented with Wess-Zumino-Witten terms. We argue that the Stiefel liquids form a class of critical quantum liquids with extraordinary properties, such as large emergent symmetries, a cascade structure, and nontrivial quantum anomalies. We show that the well known deconfined quantum critical point and U(1) Dirac spin liquid are unified as two special examples of Stiefel liquids, with N=5 and N=6, respectively.Furthermore, we conjecture that Stiefel liquids with N>6 are non-Lagrangian, or in other words are beyond any mean-field descriptions including parton constructions. We further predict that the some of the non-Lagragian Stiefel liquids can be realized as a critical spin liquid in frustrated quantum spin systems, for example, on triangular or kagome lattice, through the intertwinement between non-coplanar magnetic orders and valence-bond-solid orders.

 

Host

Yasu Takano

 

February 8   

 

Speaker

Yi Li (Johns Hopkins Univ.)

 

Title

Topological superconducting and many-body orders in doped semimetals

Abstract

Electrons in a material can synchronize to exhibit collective effects and various ordered states. I will discuss novel superconducting and density wave orders which capture the topology of the gap function rather than that of quasiparticle states only. The nontrivial geometric phases of Cooper pairs and their non-Abelian generalization lead to fundamentally new topological pairing orders.

Host

Yuxuan Wang

 

February 15      

 

Speaker

 

Title

 

Abstract

 

Host

 

February 22

 

Speaker

 

Title

 

Abstract

 

Host

 

March 1 

 

Speaker

Jukka Pekola (Aalto Univ., Finland)

 

Title

Quantum thermodynamics on superconducting circuits

 

Abstract

I will start by introducing ideas and principles of how to realize thermodynamic phenomena and devices in circuits composed of superconducting elements, including qubits, combined with heat baths formed of on-chip electronic reservoirs. This way we have demonstrated quantum-limited heat transport by microwave photons [1,2], quantum heat valves [3] and rectifiers [4] and ultrasensitive calorimetric detectors [5]. Towards the end of the talk I will present how we plan to realize quantum heat engines and refrigerators based on thermodynamic cycles [6] and considerations on ultimate energy resolution of nanocalorimeters [5,7,8].

[1] M. Meschke, W. Guichard, and J.P. Pekola, Nature 444, 187 (2006). [2] A.V. Timofeev, M. Helle, M. Meschke, M. Möttönen, and J.P. Pekola, Phys. Rev. Lett. 102, 200801 (2009). [3]  A. Ronzani, B. Karimi, J. Senior, Y.-C. Chang, J. T. Peltonen, C.D. Chen, and J.P. Pekola, Nat. Phys. 14, 991 (2018). [4] J. Senior, A. Gubaydullin, B. Karimi, J.T. Peltonen, J. Ankerhold, J.P. Pekola, Comm. Phys. 3, 40 (2020). [5] B. Karimi, F. Brange, P. Samuelsson, and J. P. Pekola, Nat. Commun. 11, 367 (2020). [6] B. Karimi and J. P. Pekola, Phys. Rev. B 94, 184503 (2016). [7] B. Karimi and J.P. Pekola, Phys. Rev. Lett. 124, 170601 (2020). [8] J. P. Pekola and B. Karimi, in preparation.

 

Host

Yasu Takano

 

March 8 

Speaker

Wei Xue (UF)

 

Title

Superfluid effective field theory

 

Abstract

In this talk, I will present new developments in an effective field theory (EFT) of helium superfluid. One of the motivation to build this framework is to understand a test particle scattering of the superfluid with its de Broglie wavelength shorter than the average helium spacing. The scattered helium atom will produce a few to thousands of quasi-particles. Due to mixing with different momentum scales, a naive EFT of the superfluid breaks down, but a novel EFT is introduced to describe how helium atoms decay to quasi-particles and quasi-particles are thermalized.

 

Host

Tarek Saab

 

March 15      

 

Speaker

 

Title

 

Abstract

 

Host

 

March 22 

 

Speaker

Pinshane Huang (Univ. Illinois Urbana-Champaign)

 

Title

How stiff are 2D materials? Designing ultrasoft electronic materials using insights from electron microscopy

 

Abstract

Understanding the deformation and bending of two-dimensional (2D) materials is critical for the realization of next-generation electronics and nanomechanical devices. For example, while the mechanics of few-layer graphene have been studied for more than a decade, there is still no consensus on basic properties such as its bending stiffness and how it scales with thickness.  In addition, defect and strain engineering of 2D materials is an emerging area of research, where homogeneous or heterogeneous alloying can stabilize exotic electronic phases such as Weyl semimetals or pattern the properties of 2D nanoelectronics and optoelectronics on the nanoscale. Electron microscopy provides a powerful platform for addressing these challenges by enabling measurements of the conformation and strain of 2D materials at atomic resolution. In this talk, I will discuss our work using aberration-corrected scanning transmission electron microscopy (STEM) in order to probe and quantify these deformations in 2D materials at the atomic scale.  This work is divided into two areas: 1) using machine learning to expand the precision of atomic resolution STEM in order to visualize local picometer-scale strain fields and understand how single-atom defects interact with the surrounding lattice and 2) using STEM in combination with mechanical modeling to reveal an unusual, slip-mediated softening of graphene and other 2D materials. Our results indicate that the bending stiffness of few layer graphene can be orders of magnitude smaller than previously thought and provide a new lower limit for the fabrication of ultra-soft, high mobility electronic nanodevices based on 2D materials. As a bonus, I will also talk about our recent work imaging small molecules at atomic resolution on graphene substrates.

 

Host

Kathryn McGill

 

March 29 

 

Speaker

Eduardo Fradkin (Univ. Illinois Urbana-Champaign)

 

Title

Duality in condensed matter and high energy physics

 

Abstract

I will discuss the subject of duality transformations in condensed matter and in high energy physics both from a historical and modern perspectives. I will focus on the role of recently discovered dualities in 2+1 dimensions in the problem of the quantum Hall plateau transitions and in the theories of non-Abelian quantum Hall states.

 

Host

Yuxuan Wang

 

April 5 

 

Speaker

 

Title

 

Abstract

 

Host

 

April 12 

 

Speaker

Serena Bradde (American Physical Society)

 

Title

The dimension of a complex system: a physicist perspective

 

Abstract

A fundamental problem in science is uncovering the effective number of dynamical degrees of freedom in a complex system. For many real systems, the dimension changes on the spatio-temporal scale at which the system is observed, making the problem of dimensional reduction hard to solve. In this talk, I will propose an approach to describe ‘effectively’ the behavior of complex systems by drawing an analogy with the Renormalization Group.

 

Host

Purushottam Dixit

 

April 19 

 

Speaker

 

Title

 

Abstract

 

Host