Chiral-Structured Superconductors TrX4 (Tr = Rh, Ir; X = Ge, Si): A Platform for Mixed-Parity Pairing and Topological States
Zhenhai Yu, Yunguan Ye, Yuwei Zhou, Chaoyang Chu, Congcong Le, Lin Wu, Jian Yuan, Tong Shi, Qingxin Dong, Jinggeng Zhao, Wei Xia, Xiangqi Liu, Xia Wang, Bosen Wang, Jinguang Cheng, Yanhang Ma, Xianxin Wu, Xiangang Wan, Huiqiu Yuan, Yanfeng GuoAbstract
Chiral-structured superconductors, with simultaneous broken mirror and inversion symmetries, promote unconventional superconductivity through parity-mixing mechanisms. Yet a few bulk chiral-structured superconductors are known, partly due to the difficulty in directly determining their atomic-scale chirality. Here, we report three chiral-structured superconductors, RhGe4, IrGe4, and IrSi4, synthesized under high pressure, with Tc values of ∼2.6, 1.1, and 2.5 K, respectively. Using atomic-resolution Cs-corrected scanning transmission electron microscopy (STEM) combined with X-ray diffraction characterizations, we directly confirm their chiral structure (space group P3121). This real-space imaging approach overcomes ambiguities in traditional diffraction-based methods. These materials exhibit type-II superconductivity, and the enhancement of spin–orbit coupling (SOC) leads to the emergence of mixed-parity pairing. Calculations also reveal symmetry-protected Weyl points near the Fermi level, which is robust against the SOC. Our work not only expands the family of chiral-structured superconductors but also demonstrates the indispensable role of STEM in directly determining chiral crystal structures. These materials thus offer a clean platform to explore the interplay among structural chirality, spin–orbit coupling, mixed-parity superconductivity, and topological quantum phenomena.