Coherent Light Control of a Metastable Hidden Phase

TL;DR

This study demonstrates ultrafast, coherent control of a hidden metastable phase in 1T-TaS2 using light, revealing nonthermal transition dynamics and paving the way for ultrafast device applications.

Contribution

It introduces a method to coherently control the formation of a hidden phase in a layered material using double-pulse excitation.

Findings

Nonthermal phase transition governed by charge-density-wave excitation

Vibrational coherent control enhances phase-switching efficiency

Achieved rapid, stable switching of the hidden phase

Abstract

Metastable phases present a promising route to expand the functionality of complex materials. Of particular interest are light-induced metastable phases that are inaccessible under equilibrium conditions, as they often host new, emergent properties switchable on ultrafast timescales. However, the processes governing the trajectories to such hidden phases remain largely unexplored. Here, using time- and angle-resolved photoemission spectroscopy, we investigate the ultrafast dynamics of the formation of a hidden quantum state in the layered dichalcogenide 1T-TaS$_2$ upon photoexcitation. Our results reveal the nonthermal character of the transition governed by a collective charge-density-wave excitation. Utilizing a double-pulse excitation of the structural mode, we show vibrational coherent control of the phase-transition efficiency. Our demonstration of exceptional control, switching speed, and stability of the hidden phase are key for device applications.