4 papers
On the Symmetries of Anisotropic Spin Interaction Models
Arist Zhenyuan Yang
We show that anisotropic spin interactions do not merely break spin-space group (SSG) symmetries, but instead twist them through cohomology invariants, yielding symmetry classes be…
Spin-Charge Groups for Fermions in Fluids and Crystals: General Structures and Physical Consequences
Arist Zhenyuan Yang, Zheng-Xin Liu
Known symmetry groups are insufficient to describe the various couplings among spin, charge, and spatial degrees of freedom in fermionic systems. To address this problem, we introd…
Constructions and Applications of Irreducible Representations of Spin-Space Groups
Ziyin Song, A. Z. Yang, Yi Jiang +5
Spin-space groups (SSGs), including the traditional space groups (SGs) and magnetic space groups (MSGs) as subsets, describe the complete symmetries of magnetic materials with weak…
Representation Theory for Massless Quasiparticles in Bogoliubov-de Gennes Systems
Arist Zhenyuan Yang, Zheng-Xin Liu
Gapless quasiparticles can exist in the Bogoliubov-de Gennes (BdG) Hamiltonians in the mean field description of superconductors (SCs), fermionic superfluids (SFs) and quantum spin…