PHYSICS DISSERTATION DEFENSE: Jacob Marks
Ph.D. Candidate: Jacob Marks
Research Advisor: Tom Devereaux
Co-advisor: Xiaoliang Qi
Time: 4 PM PDT
Location: McCullough 335
Zoom Link: https://stanford.zoom.us/j/91233225659
Zoom Password: email email@example.com for password.
Title: The Surprising Persistence of Symmetry Protected Topology
Abstract: In 1980, while subjecting semiconductors at low temperatures to strong magnetic fields, Klaus von Klitzing observed a surprising exact quantization in transverse resistivity. This phenomenon, which has been confirmed to three parts per ten billion, was subsequently explained by the integer quantum Hall effect, forever altering our understanding of what is possible in correlated electron materials.
In the first part of my talk, I will introduce topology, the branch of mathematics that underpins this phenomenon. I’ll speak about topological materials and their applications, and I’ll compare topological order with the Landau symmetry breaking paradigm. I’ll end this section by introducing symmetry protected topology, which is responsible for all topological insulators and superconductors, and highlighting the rigidity of established frameworks for categorizing this physics.
The remainder of my talk will argue for the inadequacy of these frameworks in explaining the robustness of symmetry protected topological phenomena. Focusing on the paradigmatic model for a topological insulator, the Su-Schrieffer-Heeger model, I will discuss two scenarios in which signatures of topology persist beyond the established frameworks. First, I will show that quantized charge transport is still possible when protecting symmetries are broken. Second, I will demonstrate that even out of equilibrium, signatures of topology can be identified on both single particle and many body levels. I will conclude with a brief outlook.