Ultrafast melting of a charge-density wave in the Mott insulator 1T-TaS2

TL;DR

This study uses femtosecond spectroscopy to observe ultrafast melting of charge order in 1T-TaS2, revealing rapid phase transition dynamics at atomic site resolution.

Contribution

It demonstrates atomic-site specific measurement of charge-density-wave melting dynamics using free-electron laser spectroscopy.

Findings

Charge order is lost promptly after photoexcitation.

System transitions to a short-range ordered state within 1 ps.

Method enables detailed study of nonequilibrium condensed matter dynamics.

Abstract

Femtosecond time-resolved core-level photoemission spectroscopy with a free-electron laser is used to measure the atomic-site specific charge-order dynamics in the charge-density-wave/Mott insulator 1T-TaS2. After strong photoexcitation, a prompt loss of charge order and subsequent fast equilibration dynamics of the electron-lattice system are observed. On the time scale of electron-phonon thermalization, about 1 ps, the system is driven across a phase transition from a long-range charge ordered state to a quasi-equilibrium state with domain-like short-range charge and lattice order. The experiment opens the way to study the nonequilibrium dynamics of condensed matter systems with full elemental, chemical, and atomic site selectivity.