Electronic Coherence Evolution at the Nearly Commensurate Incommensurate CDW Boundary of 1T-TaS2

TL;DR

This study uses temperature-dependent ARPES to investigate the electronic structure changes in 1T-TaS2 near the nearly commensurate-incommensurate CDW transition, revealing a coherence loss and Fermi surface reshaping without a full band gap opening.

Contribution

It provides the first momentum-resolved insight into the electronic reconstruction at the CDW transition in 1T-TaS2, challenging the conventional metal-insulator transition view.

Findings

Suppression of quasiparticle spectral weight at the Brillouin zone center.

No clear evidence of a full band gap opening.

Momentum-dependent spectral weight redistribution indicating loss of coherence.

Abstract

Transition metal dichalcogenides host a variety of charge density wave phases that couple lattice, charge, and correlation effects. In 1T-TaS2, the commensurate and nearly commensurate states are well characterized, yet the transition near 350 K into the incommensurate phase has lacked direct momentum resolved insight. Here we use temperature dependent angle resolved photoemission spectroscopy to track the electronic structure across this transition. We observe a suppression of quasiparticle spectral weight at the Brillouin zone center, coincident with the transport anomaly, but without clear evidence of a full band gap opening. The transition appears to involve momentum dependent redistribution of spectral weight, consistent with a loss of coherence that reshapes the Fermi surface while leaving conduction dispersions largely intact. These results suggest that the nearly commensurate incommensurate transition may not align with a conventional metal insulator transition picture, but rather as an electronic reconstruction driven by loss of coherence. Our work provides new microscopic insight into the resistivity anomaly near room temperature and may guide design principles for collective electronic switching in Transition metal dichalcogenides.