周期场驱动下量子材料的非平衡物态

Nonequilibrium states in quantum materials under time-period driving

量子材料的拓扑物态的研究是当前凝聚态物理的重要前沿.区别于局域对称性破缺对物质状态进行分类的传统方式,量子物态可以用微观体系波函数的拓扑结构进行分类.这些全新的拓扑物态有望颠覆传统的微电子学并进而推动拓扑电子学的迅猛发展.当前大部分理论和实验研究集中于研究量子材料的平衡态性质.周期性光场驱动下量子材料远离平衡态、而达到非平衡态时的拓扑物态近年来受到人们的广泛关注.本文首先回顾周期场驱动下非平衡态的弗洛凯(Floquet)理论方法,分别介绍无质量(如石墨烯)、有质量(如MoS_(2))等狄拉克费米子材料体系在远离平衡态下的拓扑物态,利用光场与量子物态的相干耦合实现对量子材料非平衡物态的调控;从原子制造角度出发,光场诱导的相干声子态直接改变了量子材料中电子跃迁的大小,进而调控量子材料的非平衡拓扑物态.量子材料中丰富的声子态为非平衡拓扑物态的调控提供了更多的可能性.最后,文章展望了量子材料非平衡拓扑物态在超快相变以及瞬态物态调节等未来可能发展方向的应用.

The topology of quantum materials is the frontier research in condensed matter physics.In contrast with the conventional classification of materials by using the local symmetry breaking criterion,the states of quantum systems are classified according to the topology of wave functions.The potential applications of topological states may lead the traditional microelectronics to break through and accelerate the significant improvement in topological electronics.Most of the recent studies focus on the topological states of quantum systems under equilibrium conditions without external perturbations.The topological states of quantum systems far from the equilibrium under time-periodic driving have attracted wide attention.Here we first introduce the framework of Floquet engineering under the frame of the Floquet theorem.The nonequilibrium topological states of massless and massive Dirac fermions are discussed including the mechanism of phase transition.Light field driven electronic transition term in the quantum material gains extra time-dependent phase.Thereby the manipulation of effective transition term of the electron is realized to regulate the non-equilibrium topological states.We also mention how the photoinduced coherent phonon affects the nonequilibrium topological states of quantum systems from the perspective of atom manufacturing.Furthermore,research outlook on the nonequilibrium topological states is given.This review provides some clues to the design of physical properties and transport behaviors of quantum materials out of equilibrium.