A Comment on the Origin of Conductance Dips at Finite Bias in Andreev Reflection Spectroscopy Data

TL;DR

This paper clarifies the origin of conductance dips at finite bias in Andreev reflection spectra, challenging previous interpretations and emphasizing the importance of accurate spectroscopic analysis in topological superconductor research.

Contribution

It provides a corrected understanding of conductance dips in AR spectra, impacting interpretations of topological superconductivity in CuxBi2Se3.

Findings

Double-peak AR spectra observed in experiments.

Absence of zero-energy Majorana fermions in CuxBi2Se3.

Clarification that conductance dips do not preclude spectroscopic analysis.

Abstract

In an experimental study of Andreev reflection (AR) in normal metal/superconductor (N-S) devices featuring a superconducting topological insulator CuxBi2Se3 [arXiv:1301.1030], Peng et. al. reported the reproducible experimental observation of archetypical double-peak AR spectra for finite barrier strength in N-S junctions, which clearly indicates the absence of zero-energy peak in density of states and thus rules out theoretically predicted zero-energy Majorana fermions in CuxBi2Se3. This report casts doubt on previous claims of CuxBi2Se3 as a topological superconductor. Here we clarify an inaccurate understanding which claims that no spectroscopic information can be extracted from N-S point-contacts showing conductance dips at finite bias. Such a clarification of the origin of conductance dips in AR spectra is important for future research in this field.