Anisotropic Charge Density Waves in Thermal Quench of 2<i>H</i>-TaSe₂

Transition-metal dichalcogenides such as 2H-TaSe₂, known for various charge density waves (CDWs), have attracted renewed attention for their variety of nonequilibrium CDW states, including the hidden states [1]. Nakatsugawa et.al. [2] reinvestigated the phenomenological Ginzburg-Landau (GL) model for CDWs in 2d within a constrained order-parameter (OP) manifold, finding many metastable states including stripe-CDW states. There remain two questions: whether other metastable states exist outside the constrained manifold and what metastable states among others are realizable by physical perturbations such as thermal quench. To answer these questions, we performed a real-space time-dependent GL simulation for 2H-TaSe₂, without constraint on OP configurations. Temperature sweeping with white thermal noise was considered, and an anisotropic CDW with lowered symmetry was found under strong noise, although the model was initially fully symmetric. Thus, our time-dependent GL approach is useful for describing CDW dynamics and finding new states and contributes to the unified understanding of various CDWs including the hidden ones.

[1] L. Stojchevska et al., Science 344, 177 (2014).
[2] K. Nakatsugawa et al., Sci. Rep. 10, 1239 (2020).