Spring 2020

The Sounds of Quantum Fermi Fluids

Inti Sodemann
Monday, February 3, 2020 - 3:30pm

Ordinary classical fluids have a single type of sound waves consisting of longitudinal compressional oscillations of the density. Solids, on the other hand, have also transverse or shear sound waves because of their non-zero restoring force to shear deformations. In this talk, I will illustrate that quantum fermi liquids can radically deviate from this paradigm by developing a sharp collective transverse or shear sound wave when their interactions increase beyond a threshold, even though their ground state remains in a liquid state without any form of proper static crystalline order. I...

Topology and correlations in two-dimensional systems

Mathias Scheurer
Monday, January 13, 2020 - 3:30pm

Mathias Scheurer is a postdoctoral fellow working on theoretical condensed matter in Prof. Subir Sachdev's group at Harvard University.

Abstract: Two-dimensional (2D) systems have become a very active field of research due to their particularly rich physics. As we know from classical statistical mechanics, 2D systems are special as they are situated right at the lower critical dimension and, as such, just incapable of spontaneously breaking a continuous symmetry at finite temperature. Nonetheless, finite-temperature phase transitions are possible; these are, however, not...

The Search for Topological Phases of Matter

Ashley Cook
Thursday, January 9, 2020 - 3:30pm

Ashley Cook is a postdoctoral researcher in condensed matter theory in the group of Prof. Joel Moore at UC Berkeley.

Abstract: In our daily lives, we encounter phases of matter distinguished by the symmetries they break, such as steam and ice. Such phases are well-understood with very established theory of Ginzburg and Landau, suggesting the work to characterize and understand phases of matter might be close to completion. In the 1980's, however, physicists were confronted with the integer and fractional quantum Hall effects, phases of matter that cannot be...

Josephson Detection of Multiband Effects in Superconductors

James Williams
Thursday, January 16, 2020 - 4:00pm

The study of unconventional superconducting materials remains an active frontier of condensed matter physics. Exotic superconductivity, such as high TC, topological, and heavy-fermion superconductors, often rely on phase sensitive measurements to determine the underlying pairing and/or the nature of novel excitations. In this talk I will detail the use of Josephson effect to detect novel properties of two multiband superconducting systems: NbSe2 [1] and SnTe [2]. Focus will primarily be given modification of conventional Josephson effects due to the loss of time...