Charge transfer and Spin-Valley locking in 4Hb-TaS$_{2}$

TL;DR

This study uncovers how charge transfer and reduced inter-layer coupling in 4Hb-TaS$_{2}$ lead to unique electronic properties, including spin-valley locking, which are distinct from its constituent layers and relevant for topological and magnetic phenomena.

Contribution

It provides the first detailed angle-resolved photoemission spectroscopy analysis revealing charge transfer and spin-valley locking in 4Hb-TaS$_{2}$, a heterostructure superconductor.

Findings

Significant charge transfer from 1T to 1H layers alters band structure.

Reduced inter-layer coupling enhances spin-valley locking.

Distinct electronic structure compared to constituent materials.

Abstract

4Hb-TaS$_2$ is a superconductor that exhibits unique characteristics such as time-reversal symmetry breaking, hidden magnetic memory, and topological edge modes. It is a naturally occurring heterostructure comprising of alternating layers of 1H-TaS$_2$ and 1T-TaS$_2$. The former is a well-known superconductor, while the latter is a correlated insulator with a possible non-trivial magnetic ground state. In this study, we use angle resolved photoemission spectroscopy to investigate the normal state electronic structure of this unconventional superconductor. Our findings reveal that the band structure of 4H-TaS$_2$ fundamentally differs from that of its constituent materials. Specifically, we observe a significant charge transfer from the 1T layers to the 1H layers that drives the 1T layers away from half-filling. In addition, we find a substantial reduction in inter-layer coupling in 4Hb-TaS$_2$ compared to the coupling in 2H-TaS$_2$ that results in a pronounced spin-valley locking within 4Hb-TaS$_2$