An experimental algorithm for identifying the topological nature of Kondo and mixed valence insulators

TL;DR

This paper proposes an experimental algorithm combining advanced ARPES techniques to determine the topological nature of surface states in Kondo and mixed valence insulators, specifically applied to SmB6, revealing evidence of topological surface states.

Contribution

It introduces a systematic experimental methodology using high-resolution ARPES to identify topological surface states in Kondo insulators, addressing limitations of previous studies.

Findings

Surface Fermi surface topology in SmB6 is consistent with topological predictions.

Low temperature, ultra-high resolution ARPES reveals potential topological surface states.

Methodology distinguishes between topological and trivial surface states in complex insulators.

Abstract

Possible topological nature of Kondo and mixed valence insulators has been a recent topic of interest in condensed matter physics. Attention has focused on SmB6, which has long been known to exhibit low temperature transport anomaly, whose origin is of independent interest. We argue that it is possible to resolve the topological nature of surface states by uniquely accessing the surface electronic structure of the low temperature anomalous transport regime through combining state-of-the-art laser- and synchrotron-based angle-resolved photoemission spectroscopy (ARPES) with or without spin resolution. A combination of low temperature and ultra-high resolution (laser) which is lacking in previous ARPES studies of this compound is the key to resolve the possible existence of topological surface state in SmB6. Here we outline an experimental algorithm to systematically explore the topological versus trivial or mixed (topological and trivial surface state admixture as in the first 3D TI Bi$_{1-x}$Sb$_x$) nature of the surface states in Kondo and mixed valence insulators. We conclude based on this methodology that the observed topology of the surface Fermi surface in our low temperature data considered within the level of current resolution is consistent with the theoretically predicted topological picture, suggesting a topological origin of the dominant in-gap ARPES signal in SmB6.}