Zero-energy Andreev bound states in iron-based superconductor Fe(Te,Se)

TL;DR

This paper demonstrates that zero-energy peaks observed in Fe(Te,Se) superconductors can be explained by trivial Andreev bound states caused by surface inhomogeneities, challenging their interpretation as Majorana states.

Contribution

It shows that inhomogeneities and impurities can produce zero-energy peaks mimicking Majorana states, emphasizing the need for careful analysis in topological superconductor experiments.

Findings

Zero-energy bias peaks can originate from trivial ABSs.

ABSs behave similarly to Majorana bound states in simulations.

Surface inhomogeneities are crucial in interpreting experimental results.

Abstract

Majorana bound states have been predicted to exist in vortices of topological superconductors (SC). A realization of the Fu-Kane model, based on a three-dimensional topological insulator brought into proximity to an $s$-wave SC, in iron-based SC Fe(Te,Se) has attracted strong interest after pronounced zero-energy bias peaks were observed in several experiments. Here, we show that, by taking into account inhomogeneities of the chemical potential or the presence of potential impurities on the surface of Fe(Te,Se), the emergence of these zero-energy bias peaks can be explained by trivial Andreev bound states (ABSs) whose energies are close to zero. Our numerical simulations reveal that the ABSs behave similarly to Majorana bound states. ABSs are localized only on the, say, top surface and cannot be distinguished from their topological counterparts in transport experiments performed with STM tips. Thus, such ABSs deserve a careful investigation of their own.