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Non-equilibrium quantum liquids of periodically driven fermions(周期驱动费米子的非平衡量子液体)

发布日期:2024-08-07 作者: 编辑:内容维护管理员3 来源:兰州理论物理中心

主讲人:Inti Sodemann Villadiego 教授(莱比锡大学)

目:Non-equilibrium quantum liquids of periodically driven fermions(周期驱动费米子的非平衡量子液体)

间:2024年8月12日(周一)上午10:00

地点:理工楼1226

联系人:陈川

报告摘要:

When fermions are in equilibrium with a heat bath they occupy states according to the well-known Fermi-Dirac distribution. When the bath is very cold, this distribution displays a discontinuous jump defining the location of the Fermi surface. But how should fermions occupy states when they are driven away from equilibrium by a time dependent periodic force? would their occupation still have sharp jumps? or would the periodic drive simply heat them up and smear their fermi surfaces?

当费米子与热库处于平衡状态时,它们遵从众所周知的费米-狄拉克分布占据状态。当热库非常冷时,这种分布显示出定义费米面位置的不连续跳跃。但是,当费米子受到时间依赖的周期性驱动力而远离平衡状态时,它们应该如何占据状态?它们的占据状态是否仍然会有明显的跳跃?还是周期性驱动会简单地加热它们并使它们的费米面模糊?

Recent investigations have revealed that the non-equilibrium steady states of periodically driven fermions can retain sharp fermi surfaces and remain much more quantum than previously anticipated. Interestingly, the non-equilibrium steady states of fermions can be very different in a grand-canonical setting where the system exchanges particles and energy with the bath (i.e. fermions coupled to a fermionic bath) and a canonical setting where the system only exchanges energy with the bath (i.e. fermions coupled to a bosonic bath). In the grand-canonical setting there is a non-equilibrium fermi-liquid-like steady state with an occupation that displays multiple jumps resembling a staircase shape, and therefore features multiple non-equilibrium fermi surfaces. In contrast, in the canonical setting there is a non-equilibrium non-fermi-liquid steady state where the occupation does not have jumps but rather multiple sharp kinks, which, remarkably, remain sharp even when the bath is at finite temperature. Some of the platforms and regimes to realize experimentally these states are readily accessible, and include ultra-clean and cold two-dimensional metallic systems such as Gallium arsenide hetero-structures or graphene irradiated with microwaves.

最近的研究表明,周期驱动费米子的非平衡稳态可以保持清晰的费米面,并且比预期的更具量子特性。有趣的是,费米子的非平衡稳态在巨正则系综和正则系综中的表现可以非常不同。在巨正则系综中,系统与热库交换粒子和能量(即费米子与费米子热库耦合),而在正则系综中,系统只与热库交换能量(即费米子与玻色子热库耦合)。在巨正则系综中,存在一种类似非平衡费米液体的稳态,其占据状态显示出类似阶梯形状的多重跳跃,因此具有多个非平衡费米面。相反,在正则系综中,存在一种非平衡的非费米液体稳态,其占据状态没有跳跃,而是表现出多个明显的折点,这些折点在热库处于有限温度时仍然保持清晰。一些实现这些状态的实验平台和条件非常容易获得,包括超洁净低温的二维金属系统,如镓砷化物异质结构或用微波辐照的石墨烯。

个人简介:

Prof. Inti Sodemann Villadiego obtained his PhD from the University of Texas at Austin, and conducted postdoctoral research as a Pappalardo fellow at MIT. He later served as a group leader at the Max Planck Institute for the Physics of Complex Systems before assuming his current position as a professor at the Institute for Theoretical Physics at the University of Leipzig. Prof. Sodemann Villadiego’s research is mainly about: fractionalized and topological phases of matter such as quantum Hall and spin liquids; quantum transport and non-equilibrium phenomena especially those involving Berry phase; non-perturbative methods for strongly interacting phases of matter.

Inti Sodemann Villadiego教授在德克萨斯大学奥斯汀分校获得博士学位,并在麻省理工学院(MIT)担任Pappalardo博士后研究员。他后来在位于德国德累斯顿的马克斯普朗克复杂系统物理研究所担任研究组组长,然后担任莱比锡大学理论物理研究所教授。Sodemann Villadiego教授的研究主要涉及:分数量子霍尔效应和自旋液体等物质的拓扑相、量子输运和涉及Berry相的非平衡现象、以及强相互作用物质相的非微扰方法。

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