Colloquiums INC 2023: “Searching for topological phases of matter and their electromagnetic signatures”
Title: “Searching for topological phases of matter and their electromagnetic signatures”
When: 23 October 2023, 12:00
Where: Facultad de Ciencias, Sala de Grados, Módulo 8
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 some comments on the remarkable recent progress in using quantum computers and emulators to create topological states.