Coexistence of near- E F Flat Band and Van Hove Singularity in a Two-Phase Superconductor

作者：Xuezhi Chen, Le Wang, Jun Ishizuka, Renjie Zhang, Kosuke Nogaki, Yiwei Cheng, Fazhi Yang, Zhenhua Chen, Fangyuan Zhu, Zhengtai Liu, Jia‐Wei Mei, Youichi Yanase, Baiqing Lv, Yaobo Huang · 发表于：Physical Review X · 年份：2024 · DOI：10.1103/physrevx.14.021048 · 被引用次数：22 · 研究领域：Physics of Superconductivity and Magnetism、Iron-based superconductors research、Superconductivity in MgB2 and Alloys

Quantum many-body systems, particularly, the ones with large near- E F density states, are well known for exhibiting rich phase diagrams as a result of enhanced electron correlations. The recently discovered locally noncentrosymmetric heavy fermion superconductor CeRh 2 As 2 has stimulated extensive attention due to its unusual H − T phase diagram consisting of two-phase superconductivity, antiferromagnetic order, and possible quadrupole-density wave orders. However, the critical near- E F electronic structure remains experimentally elusive. Here, we provide this key information by combining soft-x-ray and vacuum ultraviolet (VUV) angle-resolved-photoemission-spectroscopy measurements and atom-resolved density-functional-theory ( DFT ) + U calculations. With bulk-sensitive soft x ray, we reveal quasi-2D hole and electron pockets near the E F . On the other hand, under VUV light, the Ce flat bands are resolved with the c − f hybridization persisting up to well above the Kondo temperature. Most importantly, we observe a symmetry-protected fourfold Van Hove singularity (VHS) coexisting with the Ce 4 f 5 / 2 1 flat bands at the X point, which, to the best of our knowledge, has never been reported before. Such a rare coexistence is expected to lead to a large density of states at the zo...