Paper detail

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

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.