Evolution of the Saddle Point in Antimony Telluride Homologous Superlattices

TL;DR

This study investigates the evolution of the saddle point in antimony telluride homologous superlattices with added antimonene layers, revealing the saddle point's presence and the orbital hybridization effects near the Fermi level.

Contribution

It provides experimental evidence of the saddle point in antimony telluride superlattices and elucidates the role of orbital hybridization in shifting the van Hove singularity.

Findings

Demonstrated the presence of a saddle point near the M-point.

Identified the role of Sb and Te p_z orbital hybridization.

Showed the van Hove singularity moves toward the Fermi level.

Abstract

Combining topological insulators with topological semimetals in the form of homologous superlattices is a promising approach for generating correlated quantum matter based upon Fermi level alignment with band extrema. For antimony telluride, a saddle point is predicted to occur at the M-point, while antimonene layering is predicted to move the M-point valence band towards the Fermi level. To date, the predicted saddle point at the M-point has not yet been demonstrated, and studies of antimony telluride homologous superlattices have been limited to one or two layers of antimonene added to antimony telluride. Here, we present scanning tunneling spectroscopy and angle-resolved photoemission spectroscopy studies of a series of antimony telluride homologous superlattices with two to four layers of antimonene. In addition to demonstrating the presence of a saddle point and associated van Hove singularity near the M-point, we identify the key role of Sb and Te $p_z$ orbital hybridization in driving the van Hove singularity toward the Fermi level.