title: Microscopic theory of longitudinal sound velocity in charge ordered manganites.
abstract: A microscopic theory of longitudinal sound velocity in a manganite system is reported here. The manganite system is described by a model Hamiltonian consisting of charge density wave (CDW) interaction in the e(g) band, an exchange interaction between spins of the itinerant e(g) band electrons and the core t(2g) electrons, and the Heisenberg interaction of the core level spins. The magnetization and the CDW order parameters are considered within mean-field approximations. The phonon Green's function was calculated by Zubarev's technique and hence the longitudinal velocity of sound was finally calculated for the manganite system. The results show that the elastic spring involved in the velocity of sound exhibits strong stiffening in the CDW phase with a decrease in temperature as observed in experiments.
authors.affiliation: Condensed Matter Physics Group, PG Department of Applied Physics and Ballistics, FM University, Balasore 756 019, India.
authors.forename: G C
authors.initials: GC
authors.lastname: Rout
authors.forename: S
authors.initials: S
authors.lastname: Panda