Remnant Fermi surface in the presence of an underlying instability in layered 1T-TaS_2

TL;DR

This study uses high-resolution photoemission to investigate the Fermi surface in layered 1T-TaS_2, revealing a pseudogap and a remnant Fermi surface that persists across different charge-density-wave phases, suggesting Mott localization as a key instability.

Contribution

It provides new insights into the electronic structure of 1T-TaS_2, showing a pseudogap and a remnant Fermi surface unaffected by CDW phase transitions, indicating Mott localization effects.

Findings

Pseudogap covers large FS portions in both QC and C phases.

Remnant FS retains normal state symmetry across phases.

Mott localization may drive the underlying instability.

Abstract

We report high resolution angle-scanned photoemission and Fermi surface (FS) mapping experiments on the layered transition-metal dichalcogenide 1T-TaS_2 in the quasi commensurate (QC) and the commensurate (C) charge-density-wave (CDW) phase. Instead of a nesting induced partially removed FS in the CDW phase we find a pseudogap over large portions of the FS. This remnant FS exhibits the symmetry of the one-particle normal state FS even when passing from the QC-phase to the C-phase. Possibly, this Mott localization induced transition represents the underlying instability responsible for the pseudogapped FS.