Zhang Yichen, Gao Yuxiang, Pulkkinen Aki, Guo Xingyao, Huang Jianwei, Guo Yucheng, Yue Ziqin, Oh Ji Seop, Moon Alex, Oudah Mohamed, Gao Xue-Jian, Marmodoro Alberto, Fedorov Alexei, Mo Sung-Kwan, Hashimoto Makoto, Lu Donghui, Rajapitamahuni Anil, Vescovo Elio, Kono Junichiro, Hallas Alannah M, Birgeneau Robert J, Balicas Luis, Minár Ján, Hosur Pavan, Law Kam Tuen, Morosan Emilia, Yi Ming
Department of Physics and Astronomy, Rice University, Houston, TX, 77005, USA.
New Technologies Research Center, University of West Bohemia, Plzen, 301 00, Czech Republic.
Nat Commun. 2025 May 29;16(1):4984. doi: 10.1038/s41467-025-60020-z.
Kramers degeneracy is one fundamental embodiment of the quantum mechanical nature of particles with half-integer spin under time reversal symmetry. Under the chiral and noncentrosymmetric achiral crystalline symmetries, Kramers degeneracy emerges respectively as topological quasiparticles of Weyl fermions and Kramers nodal lines (KNLs), anchoring the Berry phase-related physics of electrons. However, an experimental demonstration for ideal KNLs well isolated at the Fermi level is lacking. Here, we establish a class of noncentrosymmetric achiral intercalated transition metal dichalcogenide superconductors with large Ising-type spin-orbit coupling, represented by InTaS, to host an ideal KNL phase. We provide evidence from angle-resolved photoemission spectroscopy with spin resolution, angle-dependent quantum oscillation measurements, and ab-initio calculations. Our work not only provides a realistic platform for realizing and tuning KNLs in layered materials, but also paves the way for exploring the interplay between KNLs and superconductivity, as well as applications pertaining to spintronics, valleytronics, and nonlinear transport.
克莱默简并是具有半整数自旋的粒子在时间反演对称性下量子力学本质的一个基本体现。在手性和非中心对称非手性晶体对称性下，克莱默简并分别以魏尔费米子的拓扑准粒子和克莱默节线（KNLs）的形式出现，它们是电子与贝里相位相关物理的基础。然而，目前缺乏在费米能级处良好隔离的理想KNLs的实验证明。在此，我们建立了一类具有大伊辛型自旋轨道耦合的非中心对称非手性插层过渡金属二硫属化物超导体，以InTaS为代表，其承载理想的KNL相。我们通过自旋分辨角分辨光电子能谱、角度相关量子振荡测量和第一性原理计算提供了证据。我们的工作不仅为在层状材料中实现和调控KNLs提供了一个现实的平台，也为探索KNLs与超导性之间的相互作用以及与自旋电子学、谷电子学和非线性输运相关的应用铺平了道路。
