Photo-induced Hidden Phase of 1T-TaS2 with Tunable Lifetime

TL;DR

This study reveals a photo-induced hidden phase in 1T-TaS2 driven by ultrafast laser pulses, with a tunable lifetime, highlighting the potential for light-controlled phase transitions in novel photonic devices.

Contribution

It uncovers a new photo-induced phase in 1T-TaS2 and models its dynamics, demonstrating control over phase transition lifetimes via laser fluence.

Findings

Discovery of a laser-fluence-dependent hidden phase in 1T-TaS2.

Transition driven by photoexcited carriers and electron-phonon scattering.

Potential for ultrafast light-controlled phase transition applications.

Abstract

Phase transitions are ubiquitous, appearing at every length scale from atoms to galaxies. In condensed matter, ultrafast laser pulses drive materials to highly non-equilibrium conditions allowing transitions to new phases of matter not attainable under thermal excitation. Despite the intense scrutiny these hidden phases have received, the details of the dynamics of transition and reestablishment of the ground state remain largely unexplored. Here, we show the transition to a hidden phase of 1T-TaS2 driven by the screening of Coulombic repulsive interaction by photoexcited electrons. The temporal evolution of the coherent lattice dynamics highlights the existence of a novel phase with a laser fluence-dependent lifetime. The modeling of the dynamics reveals that the transition is caused by photo-excited carriers and it disappears at the rate of electron-phonon scattering. Our results demonstrate how femtosecond laser absorption leads to a decoupling of the electronic and lattice sub-systems, opening the way to novel states of matter, which can be controlled with light. We expect our investigation to be a starting point towards the development of novel ultrafast photonics devices, such as switches and modulators, taking advantage of fast and tunable phase transitions.