Amplitude mode-driven ultrafast transition into a hidden state in a thin film of transition metal dichalcogenide
Amplitude mode-driven ultrafast transition into a hidden state in a thin film of transition metal dichalcogenide
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振幅模式驱动的超快过渡到过渡金属二硫属化物薄膜中的隐藏态
DOI：
10.1117/12.2611742
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Yoshikawa Naotaka
中科院分区：
文献类型：
--
作者：
Shimano Ryo;Yoshikawa Naotaka
几十年来，量子材料的超快非热控制引起了越来越多的兴趣。与光激发导致材料加热并破坏低温有序相的传统知识相反，超快光源的最新发展表明，在系统达到热平衡状态之前，有可能产生破坏有序相。作为这种光致相变的一种新途径，我们研究了层状过渡金属二硫族化合物3R-Ta 1 + xSe 21中电荷密度波（CDW）相的振幅模强激发效应.通过光抽运和光探测实验，在2.3THz的最低温度下发现了与CDW相变相关的软声子模，即振幅模。当该振幅模由强太赫兹脉冲通过双光子激发过程相干驱动时，CDW阶的动态抑制表现为具有强太赫兹激发的CDW振幅模的模式软化。此外，在太赫兹频率的光学电导率谱中观察到间隙开口，表明由振幅模式激发引起的绝缘类亚稳态。差距的形成动力学随CDW振幅模的振荡而振荡，表明平衡CDW的序参量与诱导的亚稳隐态之间存在密切的相互作用。在本报告中，我们概述了最近发表在参考文献1中的上述结果。
Ultrafast non-thermal control of quantum materials has gained growing interest over decades. Contrary to the conventional knowledge that the photoexcitation causes heating of materials and destroys the low temperature ordered phases, recent developments of ultrafast light sources have shown the possibility of creating symmetry-broken ordered phases before the system reaches thermal equilibrium state. As a new route for such a light-induced phase transition, we have investigated the effect of strong excitation of amplitude mode in a charge density wave (CDW) phase in a layered transition-metal dichalcogenide compound, 3R-Ta1+xSe21. A soft phonon mode associated with the CDW phase transition, namely the amplitude mode, is identified at 2.3 THz at the lowest temperature through the optical pump and optical probe experiments. When this amplitude mode is coherently driven by an intense THz pulse through the two-photon excitation process, a dynamical suppression of the CDW order is manifested by the mode softening of the CDW amplitude mode with intense THz excitation. Furthermore, a gap opening is observed in the THz-frequency optical conductivity spectrum, indicating that an insulating-like metastable state is induced by the amplitude mode excitation. The formation dynamics of the gap synchronizes with the oscillation of CDW amplitude mode, which indicates the intimate interplay between the order parameters of the equilibrium CDW and the induced metastable hidden state. In this presentation, we overview the above results which have been recently published in Ref.1.