Angle-resolved Photoemission Spectroscopy Study on the Surface States of the Correlated Topological Insulator YbB6

TL;DR

This study uses angle-resolved photoemission spectroscopy to confirm YbB6 as a correlated topological insulator with surface states exhibiting chirality and a larger-than-expected insulating gap.

Contribution

It provides direct experimental evidence of topological surface states and their properties in YbB6, a predicted correlated topological insulator, expanding understanding of its electronic structure.

Findings

Observation of linearly dispersive surface bands at Γ and X points

Detection of chiral orbital angular momentum in surface states

Insulating gap of approximately 100 meV larger than theoretical predictions

Abstract

We report the electronic structure of YbB6, a recently predicted moderately correlated topological insulator, measured by angle-resolved photoemission spectroscopy. We directly observed linearly dispersive bands around the time-reversal invariant momenta {\Gamma} and X with negligible kz dependence, consistent with odd number of surface states crossing the Fermi level in a Z2 topological insulator. Circular dichroism photoemission spectra suggest that these in-gap states possess chirality of orbital angular momentum, which is related to the chiral spin texture, further indicative of their topological nature. The observed insulating gap of YbB6 is about 100 meV, larger than that reported by theoretical calculations. Our results present strong evidence that YbB6 is a correlated topological insulator and provide a foundation for further studies of this promising material.