Robust Majorana conductance peaks for a superconducting lead

TL;DR

This paper proposes using a superconducting lead to detect Majorana bound states via conductance peaks, achieving quantized conductance and reducing thermal broadening effects, thus improving experimental detection methods.

Contribution

It introduces a novel approach of employing a superconducting lead to observe quantized Majorana conductance peaks, enhancing detection robustness against temperature effects.

Findings

Majorana states show symmetric conductance peaks at eV=±Δ with quantized height.

Superconducting tips reveal spatial conductance plateaus for Majorana states.

The method suppresses thermal broadening, improving detection accuracy.

Abstract

Experimental evidence for Majorana bound states largely relies on measurements of the tunneling conductance. While the conductance into a Majorana state is in principle quantized to $2e^2/h$, observation of this quantization has been elusive, presumably due to temperature broadening in the normal-metal lead. Here, we propose to use a superconducting lead instead, whose gap strongly suppresses thermal excitations. For a wide range of tunneling strengths and temperatures, a Majorana state is then signaled by symmetric conductance peaks at $eV=\pm\Delta$ with quantized height $G=(4-\pi)2e^2/h$. For a superconducting scanning tunneling microscope tip, Majorana states appear as spatial conductance plateaus while the conductance varies with the local wavefunction for trivial Andreev bound states. We discuss effects of nonresonant (bulk) Andreev reflections and quasiparticle poisoning.