Modified interlayer stacking and insulator to correlated-metal transition driven by uniaxial strain in 1$T$-TaS$_{2}$

TL;DR

This study shows how uniaxial strain can transform 1T-TaS2 from an insulator to a correlated metal by modifying interlayer coupling, revealing new insights into its electronic structure and phase transitions.

Contribution

It demonstrates the impact of uniaxial strain on interlayer coupling and electronic phases in 1T-TaS2, highlighting a previously unobserved bulk stacking structure that stabilizes metallic behavior.

Findings

Uniaxial strain induces a correlated-metal phase in 1T-TaS2.

Metallic behavior emerges below the CCDW transition temperature.

Electronic structure calculations reveal a new stacking structure stabilizing the metallic phase.

Abstract

Interlayer coupling is strongly implicated in the complex electronic properties of 1$T$-TaS$_2$ , but the interplay between this and electronic correlations remains unresolved. Here, we employ angle-resolved photoemission spectroscopy (ARPES) to reveal the effect of uniaxial strain engineering on the electronic structure and interlayer coupling in 1$T$-TaS$_2$ . The normally insulating ground state is transformed into a correlated-metal phase under strain, as evidenced by the emergence of a narrow band at the Fermi level. Temperature dependent ARPES measurements reveal that the metallic behaviour only develops below the commensurate charge density wave (CCDW) transition, where interlayer dimerization produces a band-insulator in unstrained samples. Electronic structure calculations demonstrate that the correlated metallic behaviour is stabilized by a previously predicted but unobserved bulk stacking structure with a modified interlayer coupling of the Ta d$_{z^{2}}$ electrons. Our combined approach lays bare the role of correlations and interlayer coupling in 1$T$-TaS$_2$ , providing critical input for understanding superconductivity under pressure and the metastable hidden phase induced using non-equilibrium protocols in this platform material for correlated physics.