Photoexcitation Induced Quantum Dynamics of Charge Density Wave and Emergence of a Collective Mode in 1T-TaS$_2$

TL;DR

This paper uses time-dependent density functional theory to reveal how photoexcitation induces ultrafast quantum dynamics and a novel collective mode in 1T-TaS2, challenging traditional thermal models of charge density wave melting.

Contribution

It uncovers a new collective mode caused by photodoping and demonstrates nonthermal CDW melting, advancing understanding of photoinduced quantum dynamics in 1T-TaS2.

Findings

Discovery of a novel collective mode induced by photodoping

Validation of nonthermal melting of charge density wave

Identification of dynamics distinct from thermal phonon modes

Abstract

Photoexcitation is a powerful means in distinguishing different interactions and manipulating the states of matter, especially in complex quantum systems. As a well-known charge density wave (CDW) material, 1T-TaS2 has been widely studied experimentally thanks to its intriguing photoexcited responses. However, the microscopic atomic dynamics and underlying mechanism are still under debate. Here, we demonstrate photoexcitation induced ultrafast dynamics in 1T-TaS2 using time-dependent density functional theory molecular dynamics. We discover a novel collective mode induced by photodoping, which is significantly different from thermally-induced phonon mode in TaS2. In addition, our finding validates nonthermal melting of CDW induced at low light intensities, supporting that conventional hot electron model is inadequate to explain photoinduced dynamics. Our results provide a deep insight on coherent electron and lattice quantum dynamics during the formation and excitation of CDW in 1T-TaS2.