Probing a topological quantum critical point in semiconductor-superconductor heterostructures

TL;DR

This paper investigates the topological quantum critical point in semiconductor-superconductor heterostructures, proposing bulk transport measurements to distinguish topological states from trivial superconductors, supported by a theoretical framework.

Contribution

It introduces a method to identify the topological quantum critical point through bulk transport properties, overcoming the challenge of symmetry preservation at the transition.

Findings

Bulk transport properties can distinguish topological from trivial states.

Universal low-energy theory describes the topological transition.

Proposed measurements enable characterization of the TQCP.

Abstract

Quantum ground states on the non-trivial side of a topological quantum critical point (TQCP) have unique properties that make them attractive candidates for quantum information applications. A recent example is provided by s-wave superconductivity on a semiconductor platform, which is tuned through a TQCP to a topological superconducting (TS) state by an external Zeeman field. Despite many attractive features of TS states, TQCPs themselves do not break any symmetries, making it impossible to distinguish the TS state from a regular superconductor in conventional bulk measurements. Here we show that for the semiconductor TQCP this problem can be overcome by tracking suitable bulk transport properties across the topological quantum critical regime itself. The universal low-energy effective theory and the scaling form of the relevant susceptibilities also provide a useful theoretical framework in which to understand the topological transitions in semiconductor heterostructures. Based on our theory, specific bulk measurements are proposed here in order to characterize the novel TQCP in semiconductor heterostructures.