可视化Floquet-Chern绝缘体中的Berry曲率
Visualizing Berry curvature in a Floquet-Chern insulator
- University of Illinois Urbana-Champaign（伊利诺伊大学厄巴纳-香槟分校）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本文利用圆二色性Tr-ARPES直接映射Bi2Se3表面光诱导的Berry曲率，验证了Floquet-Chern绝缘体拓扑性质，为光诱导拓扑相变提供直接探测手段。
AI中文摘要：
圆偏振光可以在无带隙的Dirac系统中打开拓扑能隙，从而形成Floquet-Chern绝缘体。然而，其Berry曲率尚未被直接解析。在此，我们利用圆二色性时间分辨和角分辨光电子能谱（Tr-ARPES）来绘制Bi$_2$Se$_3$表面上Floquet-Bloch态的光诱导Berry曲率。通过比较中红外泵浦光相反螺旋度下的光谱，我们分离出诱导的几何响应。我们观察到Floquet能隙处交替符号的Berry曲率特征，这些特征以泵浦光子能量设定的间隔重复出现，并随泵浦场强重新分布，与周期性驱动Dirac哈密顿量的计算结果一致。诱导的Berry曲率和Floquet Dirac能隙的衰减速度均快于复制品强度，表明即使相干Floquet杂化减弱后，光谱复制品仍可持续存在。这些结果确立了动量分辨的Berry曲率映射作为光诱导拓扑性和相干Floquet能带形成的直接探针。
英文摘要：
Circularly polarized light can open a topological gap in a gapless Dirac system, creating a Floquet-Chern insulator. However, its Berry curvature has not been directly resolved. Here we use circular-dichroism time- and angle-resolved photoemission spectroscopy (Tr-ARPES) to map the light-induced Berry curvature of Floquet-Bloch states on the surface of Bi$_2$Se$_3$. By comparing spectra for opposite helicities of the mid-infrared pump, we isolate the induced geometric response. We observe alternating-sign Berry-curvature features at Floquet gaps that repeat at intervals set by the pump photon energy and redistribute with pump field strength in agreement with calculations for a periodically driven Dirac Hamiltonian. Both the induced Berry-curvature and the Floquet Dirac gap decay faster than the replica intensity, showing that spectral replicas can persist even after coherent Floquet hybridization weakens. These results establish momentum-resolved Berry-curvature mapping as a direct probe of light-induced topology and coherent Floquet band formation.
