Retreat from stress; Rattling in a planar coordination

Suekuni, Koichiro*; Lee, C. H.*; Tanaka, Hiromi*; Nishibori, Eiji*; Nakamura, Atsushi*; Kasai, Hidetaka*; Mori, Hitoshi*; Usui, Hidetomo*; Ochi, Masayuki*; Hasegawa, Takumi*; Nakamura, Mitsutaka   ; Kawamura, Seiko   ; Kikuchi, Tatsuya*  ; Kaneko, Koji   ; Nishiate, Hirotaka*; Hashikuni, Katsuaki*; Kosaka, Yasufumi*; Kuroki, Kazuhiko*; Takabatake, Toshiro*

Thermoelectric materials for highly efficient devices must satisfy conflicting requirements of high electrical conductivity and low thermal conductivity. In this paper, we studied the crystal structure and phonon dynamics of tetrahedrites (Cu,Zn)(Sb,As)S. The results revealed that the Cu atoms in a planar coordination are rattling, which effectively scatter phonons. These findings provide a new strategy for the development of highly efficient thermoelectric materials with planar coordination.