[19a-131-1~11] 15.7 Crystal characterization, impurities and crystal defects

[19a-131-9] A problem on the symmetry of the structure Cu₄ complex

〇Koun Shirai¹, Takayoshi Fujimura¹ (1.ISIR, Osaka Univ.)

Keywords:lattice defect, phonoluminescence, Jahn-Teller effect

A new structural model for Cu complex Cu₄ was proposed by the authors. The structure is a tetrahedron formed by four Cu with a vacancy as the center of the tetrahedron. Based on this structural model, the formation mechanism of Cu₄ complex has been studied. However, a difficulty is a discrepancy in the local symmetry between experiment (C_3v) and theory (T_d). In this study, we have shown that this discrepancy can be solved by taking the Jahn-Teller distortion into account. Although the ground state has the Td symmetry structure, the excitons of this luminescence center have degenerate states and accordingly distort the local symmetry to C_3v.