2020/04/23 by Christopher W. Peterson, Tianhe Li, Peterson, Christopher W. +7
Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #FOS: Physical sciences #Graphene research and applications #Mesoscale and Nanoscale Physics (cond-mat.mes-hall) #Photorefractive and Nonlinear Optics #Topological Materials and Phenomena
paper · pdf · doi:10.48550/arxiv.2004.11390
openalex publication_date 2020/04/23 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Topological crystalline insulators (TCIs) can exhibit unique, quantized\nelectric phenomena such as fractional electric polarization and\nboundary-localized fractional charge. This quantized fractional charge is the\ngeneric observable for identification of TCIs that lack robust spectral\nfeatures, including ones having higher-order topology. It has been predicted\nthat fractional charges can also manifest where crystallographic defects\ndisrupt the lattice structure of TCIs, potentially providing a bulk probe of\ncrystalline topology. However, this capability has not yet been confirmed in\nexperiment since measurements of charge distributions in TCIs have not been\naccessible until recently. Here, we experimentally demonstrate that\ndisclination defects can robustly trap fractional charges in TCI metamaterials,\nand show that this trapped charge can indicate non-trivial higher-order\ncrystalline topology even in the absence of any spectral signatures.\nFurthermore, we uncover a connection between the trapped charge and the\nexistence of topological bound states localized at these defects. We test the\nrobustness of these topological features when the protective crystalline\nsymmetry is broken, and find that a single robust bound state can be localized\nat each disclination alongside the fractional charge. Our results conclusively\nshow that disclination defects in TCIs can robustly trap fractional charges as\nwell as topological bound states, and moreover demonstrate the primacy of\nfractional charge as a probe of crystalline topology.\n