近日，德国慕尼黑大学的Monika Aidelsburger及其研究团队取得一项新进展。经过不懈努力，他们实现具有超冷原子的拓扑边缘模式的实空间检测和操纵。相关研究成果已于2024年6月10日在国际知名学术期刊《自然—物理学》上发表。

该研究团队提出了一种实验协议，通过在周期性调制的光晶格中改变邻近位点间的隧穿速率，成功实现了手性边缘模式的制备。特别是在周期性驱动的蜂窝晶格中，他们成功地在三种不同的Floquet拓扑体系中高效地制备了边缘模式的粒子。

通过控制势阶跃的高度和振幅，研究人员描述了边缘模式的出现及其群速度对势阶跃锐度的依赖。他们对拓扑边缘模式的直接观察为研究无序和相互作用下物质的拓扑相提供了一种工具，在这种情况下，传统的体积可观测值并不适用。

据悉，人们在周期性驱动系统中，修正了体积-边界对应关系，这是将体积拓扑不变量与边缘状态的存在联系起来的基本原理。传统的体积拓扑不变量不足以预测这类系统中拓扑边缘模式的存在。虽然超冷原子为Floquet协议的清洁实现提供了极好的设置，但到目前为止，对实空间边缘模式的观察仍颇具挑战。

附：英文原文

Title: Real-space detection and manipulation of topological edge modes with ultracold atoms

Author: Braun, Christoph, Saint-Jalm, Raphal, Hesse, Alexander, Arceri, Johannes, Bloch, Immanuel, Aidelsburger, Monika

Issue&Volume: 2024-06-10

Abstract: The bulk–boundary correspondence, a fundamental principle relating the topological invariants of the bulk to the presence of edge states, is modified in periodically driven systems. Conventional bulk topological invariants are insufficient to predict the existence of topological edge modes in such systems. Although ultracold atoms provide excellent settings for clean realizations of Floquet protocols, the observation of real-space edge modes has so far remained elusive. Here we demonstrate an experimental protocol for realizing chiral edge modes in optical lattices through the periodic modulation of the tunnelling rate between neighbouring sites. In particular, we show how to efficiently prepare particles in edge modes in three distinct Floquet topological regimes in a periodically driven honeycomb lattice. Controlling the height and amplitude of the potential step, we characterize the emergence of edge modes and the dependence of their group velocity on the sharpness of the potential step. Our direct observation of topological edge modes provides a tool to study topological phases of matter in the presence of disorder and interactions, where conventional bulk observables are not applicable.

DOI: 10.1038/s41567-024-02506-z

Source: https://www.nature.com/articles/s41567-024-02506-z