低对称ENZ导体中的受驱动时间晶体
Driven Time Crystal in Low-Symmetry ENZ Conductors
AI总结：
该研究提出低对称ENZ导体可替代透明导电氧化物，结合ENZ限域与低对称导体的强反常速度非线性，实现受驱动时间晶体响应，能克服耗散损耗并放大探测光束。
AI中文摘要：
近年来，近epsilon零（epsilon-near-zero, ENZ）材料因将场增强与强超快非线性效应相结合，在非线性光学领域受到了极大关注。尤其是氧化铟锡（ITO）等透明导电氧化物已成为一类极具前景的材料，被广泛用于利用光泵浦实现飞秒尺度变化的时间光学响应。目前文献中讨论的多数方案依赖于有效三阶非线性极化率（χ⁽³⁾）调制，其中主导的材料响应由光泵浦的包络控制。本文表明，低对称导体可作为透明导电氧化物的有趣替代方案，且能在具有光周期调制的光学系统中更自然地实现时间晶体行为。作者证明，ENZ限域结合低对称导体的强反常速度非线性，可使亚波长纳米颗粒在光泵浦下产生时间晶体响应；当泵浦强度足够高时，该响应可克服耗散损耗并引发参量放大。此外，泵浦可强烈调控弱探测光的散射与消光，极端情况下可使消光为负，此时受驱动纳米颗粒可有效放大探测光束。
英文摘要：
In recent years, epsilon-near-zero (ENZ) materials have attracted a great deal of attention in nonlinear optics, as they combine field enhancement with strong, ultrafast nonlinearities. In particular, transparent conducting oxides, such as ITO, have emerged as a promising class of materials and have been extensively exploited to achieve temporal optical responses varying on the femtosecond scale using an optical pump. Most of the solutions discussed so far in the literature rely on effective $χ^{(3)}$ modulations, wherein the dominant material response is controlled by the envelope of the optical pump. Here, it is shown that low-symmetry conductors can provide an interesting alternative to transparent conducting oxides and a more natural implementation of time-crystalline behavior in optical systems with optical-cycle modulation. I demonstrate that ENZ confinement, combined with the strong anomalous-velocity nonlinearity of low-symmetry conductors, enables a subwavelength nanoparticle to develop a time-crystalline response under optical pumping. For sufficiently strong pumping, this response can overcome dissipative losses and lead to parametric amplification. Furthermore, the pump can strongly tailor the scattering and extinction of a weak probe and, in extreme cases, render the extinction negative. In this regime, the driven nanoparticle effectively amplifies the probe beam.
