Structural Analysis of Spinel Compound CuV₂S₄ with Incommensurate Charge-Density Wave

Spinel Compound CuV₂S₄ exhibits incommensurate charge-density wave (CDW) transition at T_t ~ 90 K accompanied by a structural phase transition. We have performed synchrotron powder diffraction experiments in order to determine the crystal structure for low temperature phase. The CDW phase has an orthorhombic symmetry with the superspace group Imm2(0β0). It was found that the crystal structure is characterized by the significant change of bond lengths between vanadium atoms along a-axis. We suggested that this change is related to the orbital ordering of t_2g orbitals, which is the origin of the formation of the CDW.