Cavity quantum electrodynamics with mesoscopic topological superconductors

TL;DR

This paper demonstrates how microwave cavity measurements can detect topological phase transitions, Majorana fermions, and ground state parity in mesoscopic p-wave superconductors, revealing effects beyond simple Majorana models.

Contribution

It introduces a method to probe topological phases and Majorana fermions in superconductors via cavity quantum electrodynamics, accounting for bulk state interactions.

Findings

Cavity measurements identify topological phase transitions.

Detection of Majorana fermions through electronic susceptibility.

Observation of parity effects due to Majorana-bulk state interplay.

Abstract

We study one-dimensional $p$-wave superconductors capacitively coupled to a microwave stripline cavity. By probing the light exiting from the cavity, one can reveal the electronic susceptibility of the $p$-wave superconductor. We analyze two superconducting systems: the prototypical Kitaev chain, and a topological semiconducting wire. For both systems, we show that the photonic measurements, via the electronic susceptibility, allows us to determine the topological phase transition point, the emergence of the Majorana fermions, and the parity of their ground state. We show that all these effects, which are absent in effective theories that take into account the coupling of light to Majorana fermions only, are due to the interplay between the Majorana fermions and the bulk states of the superconductors.