Experimental search for the origin of low-energy modes in topological materials

TL;DR

This study investigates low-energy excitations in topological materials through point-contact spectroscopy, revealing a phase transition with BCS-like criticality, and explores whether these features are due to superconducting nanoparticles or a collective state at atomic steps.

Contribution

It provides experimental evidence of a BCS-type phase transition in topological materials and discusses the possible origin of low-energy modes related to atomic step states.

Findings

Observation of BCS-like criticality in differential conductance

Evidence supporting a collective state at atomic steps

Analysis of superconducting nanoparticle contribution

Abstract

Point-contact spectroscopy of several non-superconducting topological materials reveals a low temperature phase transition that is characterized by a Bardeen-Cooper-Schrieffer-type of criticality. We find such a behavior of differential conductance for topological surfaces of non-magnetic and magnetic Pb$_{1-y-x}$Sn$_y$Mn$_x$Te. We examine a possible contribution from superconducting nanoparticles, and show to what extent our data are consistent with Brzezicki's et al. theory [arXiv:1812.02168], assigning the observations to a collective state adjacent to atomic steps at topological surfaces.