Year: 2026
Type: preprint
Abstract: Crystal symmetry governs the physical properties of materials and provides the framework for interpreting their microscopic excitations and macroscopic responses. In altermagnets, the crystal symmetries that relate opposite-spin sublattices give rise to momentum-dependent spin splitting despite compensated magnetization. Determining the real crystal symmetry is therefore essential for understanding the intrinsic electronic and magnetic properties. For the altermagnetic semiconductor $α$-MnTe, conflicting Raman assignments have left both its intrinsic lattice excitations and its crystal symmetry unresolved. Here we combine high-resolution Raman and second-harmonic generation (SHG) spectroscopy with first-principles calculations to distinguish intrinsic lattice excitations from Te-derived spectral contributions and to examine bulk inversion symmetry of $α$-MnTe. We show that several prominent Raman features previously assigned to $α$-MnTe instead originate from segregated Te clusters or precipitates. The remaining intrinsic Raman response consists of a single Raman-active mode assigned to the calculated $E_{2g}$ phonon, consistent with the centrosymmetric $D_{6h}$ symmetry. The SHG response agrees with surface electric-dipole and bulk electric-quadrupole contributions expected for a centrosymmetric $D_{6h}$ crystal, supporting the preservation of bulk inversion symmetry in $α$-MnTe. Our findings revise the Raman assignments in $α$-MnTe and provide a basis for interpreting its altermagnetic properties within the appropriate crystal-symmetry framework.
Source: arXiv (Cornell University)
Authors: Cui, Yunpeng, Zhang, Shuai, Xie, Jia-Liang, Liang, Jinxuan, Lin, Hao, Qin, Miao, Shao, Jiawei, Chen, Gongling, Li, Yidian, Luo, Yixuan, Hu, Deng, Lu, Bingru, Li, Hao, Li, Xiang, Liu, Tiantian, Yu, Haodong, Zhang, Hongyun, Zhou, Shuyun, Wang, Zhiwei, Guo, Yanfeng, Zhang, Tiantian, Lin, Miao-Ling, Tan, Ping-Heng, Jin, Feng, Yang, Luyi
Institutions: State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Chinese Academy of Sciences, Institute of Theoretical Physics, Institute of Semiconductors, ShanghaiTech University, Beijing Institute of Technology, Lanzhou University, Frontier Science Center for Quantum Information of the Ministry of Education of China, Institute of Physics
Language: English
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Awards: G44998824, G8206771095, G980632040
OpenAlex ID: W7223669000