Colloquium

Searching for topological phases of matter and their electromagnetic signatures

Speaker: Joel Moore (University of California, Berkeley, and Lawrence Berkeley National Laboratory)

Date and time

Abstract

This talk starts by reviewing known examples of how topological materials generate new kinds of electrodynamic couplings and effects.  One category of topological phases can be understood in terms of nearly free electrons, but still manage to show interesting behavior such as the integer quantum Hall effect.  We start with known cases and build up to an understanding of how the recently discovered topological Weyl semimetals can show unique electromagnetic responses; in nonlinear optics there should be a new approximately quantized effect, which may have been seen experimentally.  This nonlinear effect has a natural quantum e^3/h^2 and appears in chiral Weyl semimetals over a finite window of frequencies.  We then turn to fractional topological phases and their possible appearance in frustrated magnets (the “spin liquids” proposed fifty years ago by Philip Anderson), as the past year has seen remarkable experimental and computational progress in triangular lattice materials.  We close with a few comments on the remarkable recent progress in using quantum computers and emulators to create complex states.

Joel Moore

Short Biography
Prof. Joel Moore is Chern-Simons Professor of Physics at the University of California, Berkeley, and a Senior Faculty Scientist at Lawrence Berkeley National Laboratory. His work in theoretical physics studies quantum matter with a focus on the remarkable phenomena that emerge as consequences of entanglement and topology. He received his A.B. in physics from Princeton in 1995 and spent a Fulbright year at TIFR before graduate studies at MIT. He then was a postdoc at Bell Labs before joining the Berkeley faculty in 2002. He is an elected member of the National Academy of Sciences (2022), a Simons Investigator (2013-2023), and a Fellow of the American Physical Society (2013). He previously served as member and chair of the advisory board of the Kavli Institute for Theoretical Physics.