The hidden (H) quantum state in 1T-TaS₂ has sparked considerable interest in the field of correlated electron systems. Here, we investigate ultrafast switches to stable H charge density wave (H-CDW) states observed in 1T-TaS_2-x Se _x , with x = 0 and 0.5 crystals, upon excitation with a single femtosecond laser pulse. In situ cooling transmission electron microscopy observations, initiated by a single femtosecond laser pumping with a low fluence, reveal a clear transition from a commensurate CDW phase (q_C) to a new CDW order with q_H = (1 - δ)q_C for the H-CDW state (δ = 1/9) accompanied by an evident phase separation. H-CDW domain relaxation then occurs and yields a stable metallic phase under a high-fluence excitation. Furthermore, electrical resistivity measurements show that the notable drop in x = 0 and 0.5 samples associated with the appearance of H-CDW states depend on laser fluence and temperature. These results potentially provide a new perspective on the photodoping mechanism for the emergence of H-CDW states in the 1T-TaS_2-x Se _x family.

中文翻译：

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飞秒脉冲激光激发后，在层状硫族化物1T-TaS2- x Se x中，隐藏的CDW状态和绝缘体向金属的过渡。

1T-TaS _2中的隐藏（H）量子态引起了相关电子系统领域的极大兴趣。在这里，我们研究了在单个飞秒激光脉冲激发下，在1T-TaS _{2- x} Se _x中观察到的超快切换到稳定的H电荷密度波（H-CDW）状态的过程，其中x = 0和0.5个晶体。由低通量的单飞秒激光泵浦启动的原位冷却透射电子显微镜观察表明，从相应的CDW相（q _C）明显过渡到q _H =（1-δ）q _C的新CDW级。 H-CDW状态（δ= 1/9）伴随明显的相分离。然后发生H-CDW畴弛豫，并在高通量激发下产生稳定的金属相。此外，电阻率测量结果表明，与H-CDW状态的出现有关的x = 0和0.5个样品的显着下降取决于激光通量和温度。这些结果可能为在1T-TaS _{2- x} Se _x族中出现H-CDW态的光掺杂机制提供新的观点。