Topologically quantized current in quasiperiodic Thouless pumps
Topologically quantized current in quasiperiodic Thouless pumps
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DOI：
10.1103/physrevresearch.2.042035
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发表时间：
2020-01
影响因子：
4.2
通讯作者：
P. Marra;M. Nitta
中科院分区：
文献类型：
--
作者：
P. Marra;M. Nitta
索利斯泵浦是具有量子化电荷输运的拓扑非平凡物质态，它可在加载到光学晶格中的原子气体中实现。这种拓扑态类似于量子霍尔态。然而，与霍尔电导精确且极其精确和稳定的量子化相反，只有当泵浦时间是一个特征时间尺度（即泵浦周期时长）的倍数时，泵浦电荷才严格量子化。在此，我们表明，如果系统进入准周期、不可公度态，泵浦电流会精确量子化，而与泵浦时间无关。在这种准周期且拓扑非平凡态下，布洛赫能带和贝利曲率变得平坦，泵浦电荷随时间呈线性变化，而电流变得稳定、拓扑量子化且与陈数成正比。电流的量子化是精确的，只有指数级小的修正。这必须与可公度（非准周期）态的情况形成对比，在可公度态下，电流不是恒定的，且泵浦电荷仅在泵浦周期的整数倍时才量子化。
Thouless pumps are topologically nontrivial states of matter with quantized charge transport, which can be realized in atomic gases loaded into an optical lattice. This topological state is analogous to the quantum Hall state. However, contrarily to the exact and extremely precise and robust quantization of the Hall conductance, the pumped charge is strictly quantized only when the pumping time is a multiple of a characteristic time scale, i.e., the pumping cycle duration. Here, we show instead that the pumped current becomes exactly quantized, independently from the pumping time, if the system is led into a quasiperiodic, incommensurate regime. In this quasiperiodic and topologically nontrivial state, the Bloch bands and the Berry curvature become flat, the pumped charge becomes linear in time, while the current becomes steady, topologically quantized, and proportional to the Chern number. The quantization of the current is exact up to exponentially small corrections. This has to be contrasted with the case of the commensurate (nonquasiperiodic) regime, where the current is not constant, and the pumped charge is quantized only at integer multiples of the pumping cycle.