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arXiv 1806.04733cond-mat.mes-hall
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脉冲驱动拓扑量子系统的时间分辨霍尔电导率

Time-resolved Hall conductivity of pulse-driven topological quantum systems

Lucila Peralta Gavensky, Gonzalo Usaj, C. A. Balseiro

摘要:

我们解决的问题是如何的时间分辨散装霍尔响应的二维蜂窝晶格时,驱动系统的脉冲微扰发展。一个简单的玩具模型,通过打破反转对称性切换谷霍尔信号进行了详细研究缓慢的准绝热斜坡和突然淬火,获得振荡的动态响应,强烈依赖于掺杂和时间平均值,这两个确定的平衡职业和最终状态的Berry曲率。另一方面,照射的样品与圆偏振的红外泵浦脉冲,打破时间反演对称性,从而斜坡系统到一个非平凡的拓扑制度的影响进行了探讨。尽管由于Floquet拓扑图的分解而存在非量化的平均信号,但即使在几个飞秒时间尺度内,光子修饰的拓扑带的一些特征也被揭示出来。在瞬态响应过程中的小频率振荡的证据动态Floquet间隙的出现,这是一致的泵的包络线的瞬时振幅。另一方面,在模型中表现出特征性的异染色效应。本文简要讨论了在辐射场只有几个周期的超短脉冲中存在残余霍尔响应的问题。

英文摘要:

We address the question of how the time-resolved bulk Hall response of a two dimensional honeycomb lattice develops when driving the system with a pulsed perturbation. A simple toy model that switches a valley Hall signal by breaking inversion symmetry is studied in detail for slow quasi-adiabatic ramps and sudden quenches, obtaining an oscillating dynamical response that depends strongly on doping and time-averaged values that are determined both by the out of equilibrium occupations and the Berry curvature of the final states. On the other hand, the effect of irradiating the sample with a circularly-polarized infrared pump pulse that breaks time reversal symmetry and thus ramps the system into a non-trivial topological regime is probed. Even though there is a non quantized average signal due to the break down of the Floquet adiabatical picture, some features of the photon-dressed topological bands are revealed to be present even in a few femtosecond timescale. Small frequency oscillations during the transient response evidence the emergence of dynamical Floquet gaps which are consistent with the instantaneous amplitude of the pump envelope. On the other hand, a characteristic heterodyining effect is manifested in the model. The presence of a remnant Hall response for ultra-short pulses that contain only a few cycles of the radiation field is briefly discussed.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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