Ultrafast light-matter interaction has emerged as a new mechanism to exert control over the macroscopic properties of quantum materials toward novel functionality. To date, technological applications of these non-thermal phases are limited by their ultrashort lifetimes and low-ordering temperatures. Among the most studied photoinduced metastable phases for their technological promise is the hidden metallic charge density wave (H-CDW) in the model correlated CDW compound 1T-TaS2. Despite active study and engineering, the nature of the photoinduced H-CDW remains the subject of debate and is only accessible at cryogenic temperatures. Here, we stabilize the H-CDW phase at thermal equilibrium up to near-room temperature by accessing an intermediate mixed CDW order regime via thermal quenching. Using x-ray high dynamic range reciprocal space mapping (HDRM) and scanning tunneling spectroscopy (STS), we reveal the coexistence of commensurate (C) CDW and H-CDW domains below 180 K during cooling and below 210 K during warming. 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 H-CDW phase. Despite metallic domain walls and a finite density of states at zero bias observed via STS, bulk resistance remains insulating due to CDW stacking disorder. This study establishes the H-CDW as a thermally stable phase and introduces a new mechanism for switchable metallic behavior in thin flakes of 1T-TaS2 and similar materials with competing order phases.
@article{arxiv.2407.07953,
title = {Dynamic phase transition into a mixed-CDW state in 1$T$-TaS$_2$ via a thermal quench},
author = {A. de la Torre and Q. Wang and Y. Masoumi and B. Campbell and J. V. Riffle and D. Balasundaram and P. M. Vora and J. P. C. Ruff and G. A. Fiete and S. M. Hollen and K. W. Plumb},
journal= {arXiv preprint arXiv:2407.07953},
year = {2025}
}