CONTROL OF PHONON PROPERTIES IN ELECTRON-PHONON-PROTON COUPLED SYSTEMS

In halogen-bridged mixed-valence transition-metal complexes, a new the oretical viewpoint is to control the phonon properties by taking into account the cooperative electron-proton coupling. Developing a cluster theory, proton-induced ordering is predicted to occur among one-dimen sional charge-density-wave (CDW) chains (in-phase or out-of-phase). It is discussed that the intra-chain CDW state derived from the competit ion between electron-phonon and electron-electron interactions can be changed by the proton motion on the interchain hydrogen bonds.