Leinweber Seminar: A Tale of Two Topologies ― Quantized Transport of Superconducting Topological Electronics. - Pok Man Tam, Princeton University

The study of topological phases and the study of superconductivity are two main pillars in modern quantum matter research. An exciting and timely direction is to explore the interplay between the two. When topology meets superconductivity, novel transport phenomena and new exotic phases can arise, which may benefit the development of quantum technologies in terms of robust quantum memory or computing devices. In this talk, I would like to introduce two kinds of quantized transport along this research direction.

 In the first part, the topological system concerned is the fractional quantum Hall edge, which upon disordered superconducting proximity induces an infinite family of novel superconducting edge phases, each comes with a quantized downstream resistance that can be probed in non-local transport measurement. This kind of quantized effect goes beyond the conventional Hall quantization. In the second part, I will introduce a quantized transport effect in ordinary metal-superconductor Josephson junctions. While the setup seems conventional, the unconventional transport direction along the metal-superconductor interface gives rise to a conductance-quantization that generalizes the 1D Landauer transport in quantum wires. The associated quantized transport is related to the Fermi sea topology that is ubiquitous in metals. If time allows, I will further branch out to discuss connections between Fermi sea topology and recent AMO research, as well as fundamental significance of the Fermi sea topology in terms of quantum entanglement in metals. 

The first part of the talk is based on the recent work arXiv:2505.20398, and the second part is based on PRL 130, 096301 and PRB 107, 245422.