Dynamic phase transition in 1T-TaS2 via a thermal quench

• Published in: Nature physics Vol. 21; no. 8; pp. 1267 - 1274
• Main Authors: de la Torre, Alberto, Wang, Qiaochu, Masoumi, Yasamin, Campbell, Benjamin, Riffle, Jake V., Balasundaram, Dushyanthini, Vora, Patrick M., Ruff, Jacob P. C., Fiete, Gregory A., Hollen, Shawna M., Plumb, Kemp W.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.08.2025; Nature Publishing Group
• Subjects: 639/301/1005/1007; 639/766/119/2795; 639/766/119/995; Atomic; Basal plane; Bulk density; Charge density waves; Classical and Continuum Physics; Complex Systems; Condensed Matter Physics; Cooling; Domain walls; High temperature; Low temperature; Mathematical and Computational Physics; Metastable state; Molecular; Optical and Plasma Physics; Order parameters; Phase transitions; Physics; Physics and Astronomy; Symmetry; Temperature; Theoretical; Thermal stability; Unit cell
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/s41567-025-02938-1

Ultrafast light–matter interaction has emerged as a mechanism to control the macroscopic properties of quantum materials. However, technological applications of photoinduced phases are limited by their ultrashort lifetimes and the low temperatures required for their stabilization. One such phase is the hidden metallic charge density wave state in 1T-TaS 2 , whose origin and stability above cryogenic temperatures remain the subject of debate. Here, we demonstrate that this phase can be stabilized at thermal equilibrium by accessing a mixed charge density wave order regime through thermal quenching. Using X-ray high-dynamic-range reciprocal space mapping and scanning tunnelling spectroscopy, we reveal the coexistence of commensurate charge density wave and hidden metallic charge density wave domains up to 210 K. Our findings show that each order parameter breaks basal plane mirror symmetry with different chiral orientations and induces out-of-plane unit cell tripling in the hidden phase. Despite metallic domain walls and a finite density of states, the bulk resistance remains insulating due to charge density wave stacking disorder. Our results establish the hidden state as a thermally stable phase and introduce an alternative mechanism for switchable metallic behaviour in thin flakes of 1T-TaS 2 and similar materials with competing phases. The photoinduced hidden metallic state in 1T-TaS 2 has so far been stabilized only at cryogenic temperatures. Now it is shown that accessing an additional mixed-phase long-lived metastable state can stabilize the hidden phase at higher temperatures.