Optical conductivity of the Majorana mode at the s- and d-wave topological superconductor edge

TL;DR

This paper explores how the local optical conductivity and density of states at the edge of topological superconductors reveal signatures of Majorana modes, with potential for experimental detection via microwave spectroscopy.

Contribution

It demonstrates how the symmetry of superconductivity influences optical signatures of Majorana edge states, providing guidance for future experimental observations.

Findings

Majorana edge states cause distinctive optical conductivity features.

The optical response varies with superconducting symmetry, magnetization, and temperature.

Non-monotonic temperature dependence indicates the presence of Majorana modes.

Abstract

The Majorana fermion offers fascinating possibilities such as non-Abelian statistics and non-local robust qubits, and hunting it is one of the most important topics in current condensed matter physics. Most of the efforts have been focused on the Majorana bound state at zero energy in terms of scanning tunneling spectroscopy searching for the quantized conductance. On the other hand, a chiral Majorana edge channel appears at the surface of a three-dimensional topological insulator when engineering an interface between proximity-induced superconductivity and ferromagnetism. Recent advances in microwave spectroscopy of topological edge states open a new avenue for observing signatures of such Majorana edge states through the local optical conductivity. As a guide to future experiments, we show how the local optical conductivity and density of states present distinct qualitative features depending on the symmetry of the superconductivity, that can be tuned via the magnetization and temperature. In particular, the presence of the Majorana edge state leads to a characteristic non-monotonic temperature dependence achieved by tuning the magnetization.