Experimental measurement of the Berry curvature from anomalous transport
Experimental measurement of the Berry curvature from anomalous transport
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DOI：
10.1038/nphys4050
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发表时间：
2017-06-01
期刊：
影响因子：
19.6
通讯作者：
Peschel, Ulf
中科院分区：
文献类型：
--
作者：
Wimmer, Martin;Price, Hannah M.;Peschel, Ulf
能带的几何性质是许多系统中迷人现象的基础，包括固态、超冷气体和光子学。局部几何特征，如Berry曲率（1），可以与全局拓扑不变量，如那些分类量子霍尔态或拓扑绝缘体。然而，无论能带拓扑如何，任何非零的贝里曲率都可能产生重要的后果，例如在相干波包的半经典演化中。在这里，我们的实验表明，波包动力学可以用来直接映射出的Berry曲率。为此，我们使用光脉冲在两个耦合的光纤环研究离散时间演化的波包在一维几何“电荷”泵，其中的Berry曲率导致的异常位移的波包。这既是第一次直接观察光学系统中的Berry曲率效应，也是一个原理证明，证明波包动力学可以作为绘制几何特性的高分辨率工具。
The geometric properties of energy bands underlie fascinating phenomena in many systems, including solid-state, ultracold gases and photonics. The local geometric characteristics such as the Berry curvature(1) can be related to global topological invariants such as those classifying the quantum Hall states or topological insulators. Regardless of the band topology, however, any non-zero Berry curvature can have important consequences, such as in the semi-classical evolution of a coherent wavepacket. Here, we experimentally demonstrate that the wavepacket dynamics can be used to directly map out the Berry curvature. To this end, we use optical pulses in two coupled fibre loops to study the discrete time evolution of a wavepacket in a one-dimensional geometric 'charge' pump, where the Berry curvature leads to an anomalous displacement of the wavepacket. This is both the first direct observation of Berry curvature effects in an optical system, and a proof-of-principle demonstration that wavepacket dynamics can serve as a high-resolution tool for mapping out geometric properties.