DefinePK

Abstract

Induced representation method and Mackey theorem on symmetrized squares were applied to construct zero-total-momentum two-electron states in solids, corresponding to Cooper pairs in unconventional superconductors. In this approach the structure of two-electron states depends on the position of one-electron wave vector in a single-electron Brillouin zone. It is shown, that the decomposition of total two-electron basis set results in repeating multidimensional irreducible representations. It is obtained, that in order to label repeating irreducible representation two additional quantum numbers are required: irreducible representation of wave vector group for symmetry planes and directions and quantum numbers on an intermediate group for a general point in a Brillouin zone. Theoretical results are applied to unconventional superconductors UPt3 and Sr2RuO4.