Current-Driven\nto Thermally Driven Multistep Phase\nTransition of Charge Density Wave Order in 1T-TaS<sub>2</sub>

Two-dimensional 1T-TaS<sub>2</sub> is renowned for its\nexotic physical\nproperties including superconductivity, Mott physics, flat-band electronics,\nand charge density wave (CDW) orders. In particular, the CDW phase\ntransitions (PTs) in 1T-TaS<sub>2</sub> attracted extensive research\ninterest, showing prominent potential in electronic devices. However,\nmechanisms underlying electrically driven PTs remain elusive. Here,\nwe systematically studied the evolution of multistep PTs during the <i>I</i>–<i>V</i> sweep in 1T-TaS<sub>2</sub>.\nComprehensive investigations, covering variations in temperature,\npulsed voltage duration, and light illumination, reveal that the underlying\nPT mechanism shifts from current-driven to thermally driven with increasing\ncurrent. Initially, the current-driven PT step occurs at a constant\ncurrent density, independent of the temperature. Subsequently, thermally\ndriven PT steps manifest at a constant conductivity highly sensitive\nto the thermal effect. These transitions are strongly associated with\nthe metastable CDW electronic structures and their response to carrier\ninjection and thermal variations. Our findings reconcile long-standing\ndebates regarding the electrically driven CDW PTs in 1T-TaS<sub>2</sub>.