Detecting Topological Phase Transition in Superconductor-Semiconductor Hybrids by Electronic Raman Spectroscopy

TL;DR

This paper proposes using electronic Raman spectroscopy to detect topological phase transitions in superconductor-semiconductor hybrid nanowires, overcoming challenges posed by trivial states mimicking Majorana modes.

Contribution

It introduces a novel spectroscopic method based on dynamical density response and Coulomb interactions to identify topological phase transitions in hybrid systems.

Findings

Dynamical density response reveals electronic structure changes at TPT.

Raman scattering intensities are strongly affected by the TPT.

Gapless plasmons indicate the bulk Lifshitz transition in the normal state.

Abstract

In superconductor-semiconductor hybrids, applying a magnetic field closes a trivial bulk gap and causes a topological phase transition (TPT), resulting in the emergence of Majorana zero modes at both ends of the wires. However, trivial Andreev bound states formed at the interface with metallic leads mimic the local Majorana properties, making it difficult to detect the TPT through local conductance measurements. In this work, we investigate the detection of the TPT by exploiting the static and dynamical density response of the hybrid system. In particular, we demonstrate that the dynamical renormalized responses, the density response including the effect of Coulomb interactions, reveal the characteristic electronic structure and detect the TPT, which we then show to produce strong intensities of Raman scattering. Furthermore, we find that gapless plasmons emerge in the normal state, signaling the bulk Lifshitz transition. Our results thus predict that the bulk response of superconducting nanowires is a powerful spectroscopic approach to detect the bulk topological phase transition.