Observation of a multitude of correlated states at the surface of bulk 1T-TaSe$_2$ crystals

TL;DR

This study reveals diverse correlated surface states on bulk 1T-TaSe2 crystals, including insulating Mott layers and metallic states with Kondo features, demonstrating complex electron interactions and phases within a single material.

Contribution

It uncovers multiple correlated surface states on bulk 1T-TaSe2, illustrating the material's rich electronic phases and serving as a model for correlated phenomena.

Findings

Presence of decoupled surface Mott layer.

Observation of Kondo-like zero-bias peaks.

Surface states exhibit diverse electronic ground states.

Abstract

The interplay between electron-electron interactions and structural ordering can yield exceptionally rich correlated electronic phases. We have used scanning tunneling microscopy to investigate bulk 1T-TaSe2 and have uncovered surprisingly diverse correlated surface states thereof. These surface states exhibit the same in-plane charge density wave ordering but dramatically different electronic ground states ranging from insulating to metallic. The insulating variety of surface state shows signatures of a decoupled surface Mott layer. The metallic surface states, on the other hand, exhibit zero-bias peaks of varying strength that suggest Kondo phases arising from coupling between the Mott surface layer and the metallic bulk of 1T-TaSe2. The surface of bulk 1T-TaSe2 thus constitutes a rare realization of the periodic Anderson model covering a wide parameter regime, thereby providing a model system for accessing different correlated phenomena in the same crystal. Our results highlight the central role played by strong correlations in this material family.