Nature of metallic and insulating domains in the CDW system 1T-TaSe2

TL;DR

This study investigates the electronic structure of 1T-TaSe2 in its charge density wave phase, revealing coexistence of metallic and insulating domains influenced by stacking faults and quantum size effects, with correlation effects being secondary.

Contribution

It demonstrates that stacking faults and quantum well states primarily dictate the electronic phenomena in 1T-TaSe2, highlighting the role of structural variations over correlation effects.

Findings

Coexistence of metallic and insulating regions in 1T-TaSe2

Quantum well states vary with thickness in metallic regions

Stacking faults explain the complex electronic behavior

Abstract

We study the electronic structure of bulk 1T-TaSe$_2$ in the charge density wave phase at low temperature. Our spatially and angle resolved photoemission (ARPES) data show insulating areas coexisting with metallic regions characterized by a chiral Fermi surface and moderately correlated quasiparticle bands. Additionally, high-resolution laser ARPES reveals variations in the metallic regions, with series of low-energy states, whose energy, number and dispersion can be explained by the formation of quantum well states of different thicknesses. Dynamical mean field theory calculations show that the observed rich behaviour can be rationalized by assuming occasional stacking faults of the charge density wave. Our results indicate that the diverse electronic phenomena reported previously in 1T-TaSe$_2$ are dictated by the stacking arrangement and the resulting quantum size effects while correlation effects play a secondary role.