In correlated electron materials, multiple electronic phases may appear next to each other in their phase diagram, and these can be tuned, for example, by applying static pressure or chemical doping^1,2,3. These perturbations modify the subtle balance between the electron transfer energy and Coulomb repulsion between electrons. It is, therefore, tempting to explore whether new states of matter can be accessed through the direct tuning of their order parameters, for example, by driving a collective mode of the emergent phase. Here we demonstrate that the direct excitation of the amplitude mode of a charge density wave (amplitudon) by an intense terahertz pulse in a layered transition metal dichalcogenide compound, namely, 3R-Ta_1+xSe₂, leads to the appearance of an insulating-like metastable state. The formation dynamics of the metastable phase manifest in the opening of a gap in the optical conductivity spectrum, and we show that they synchronize with an oscillation of the amplitudon. This indicates the intimate interplay between the order parameters of the equilibrium charge density wave and the metastable states.

在相关电子材料中，多个电子相可能在其相图中彼此相邻出现，并且可以通过例如施加静压或化学掺杂^1,2,3来调整这些相。这些扰动改变了电子转移能量和电子之间的库仑排斥之间的微妙平衡。因此，很容易探索新的物质状态是否可以通过直接调整它们的顺序参数来访问，例如，通过驱动涌现阶段的集体模式。在这里，我们证明了在层状过渡金属二硫属化物化合物中，即 3R-Ta _{1+ x} Se _{2中的强太赫兹脉冲直接激发电荷密度波（amplitudon）的振幅模式}，导致出现类似绝缘的亚稳态。亚稳相的形成动力学表现在光导谱中间隙的打开，并且我们表明它们与振幅的振荡同步。这表明平衡电荷密度波的有序参数与亚稳态之间的密切相互作用。