Emergence of a Fermi-surface in the current-driven Hidden state of 1T-TaS$_2$

Abstract

The origin of the insulating state in 1T-TaS$_2$ has long been a subject of debate. A short current pulse transforms this insulating state into a metastable metallic phase. Using micro-ARPES, we investigate the electronic structure of this phase and uncover spatially dependent modifications caused by the current pulse. In some regions of the sample, a Fermi surface emerges, while others remain gapped. Detailed band structure analysis reveals that the metallic regions exhibit an electronic structure similar to that observed in the high-temperature phase of 1T-TaS$_2$, characterized by suppressed energy gaps and bands crossing the Fermi level. Furthermore, the metallic and insulating regions display distinct dispersions along the out-of-plane direction. These observations suggest a scenario in which the current pulse breaks the star-of-David dimers characteristic of the insulating phase, implicating these dimers as the likely origin of the insulating behavior in 1T-TaS$_2$.