New STM Tip-induced Phases in 1T-TaS$_2$

Transition metal dichalcogenide 1T-TaS$_2$ is a layered material featuring a unique set of charge density wave (CDW) phases. The close proximity of the CDW phases in energy makes the material prone to external perturbation, and the intricate electron-phonon and electron-electron interactions often lead to electronic/structural phase transitions in 1T-TaS$_2$. Here we report a new phase transition from the insulating commensurate CDW (also known as a Mott state) to a new metallic CDW state that is induced in 1T-TaS$_2$ by voltage pulses from an STM tip at low temperatures. We study the topographic and spectroscopic properties of the metallic CDW phase in detail with STM and Scanning Tunneling Spectroscopy (STS).