Valence-lattice interaction on YbPd

International Conference on Strongly Correlated Electron Systems 2014

Hasegawa, Takumi^1 ; Ogita, Norio^1 ; Mitsuda, Akihiro^2 ; Sugishima, Masaki^3 ; Wada, Hirofumi^2 ; Tsutsui, Satoshi^4,5 ; Udagawa, Masayuki^1,5

Graduate School of Integrated Arts and Sciences, Hiroshima University, Higashi-Hiroshima

739-8521, Japan^1

Department of Physics, Kyushu University, Fukuoka

812-8581, Japan^2

Division of Technical Support, Iwate University, Morioka

020-8551, Japan^3

JASRI/SPring-8, Sayo

679-5198, Japan^4

Institute for Advanced Material Research, Hiroshima University, Higashi-Hiroshima

739-8530, Japan^5

关键词: First-principles calculation;    Incommensurate phase;    Inelastic X ray scattering;    Intermediate valence;    Lattice interactions;    Longitudinal acoustic;    Structural transitions;    Superlattice reflections;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/592/1/012061/pdf
DOI  :  10.1088/1742-6596/592/1/012061

来源: IOP

【 摘 要 】

An intermediate valence compound YbPd undergoes successive structural transitions at 105 K and 125 K. The recent inelastic X-ray scattering measurement have revealed softening of longitudinal acoustic (LA) mode around X point, q =(0, 0, 0.5). We have attempted to reproduce this softening from first-principles calculations. The calculated results with fixed valence Yb do not show any anomaly in the LA mode around X. To include valence change in the lattice vibrations, the nearest-neighbor valence-lattice interaction has been added. The interaction reduces the energy of the LA mode around X as observed by the experiment. This soft mode leads to the structure below 105 K. On the other hand, the lowest energy is found at the slightly different wavevector, q =(0.1, 0.1, 0.5). This wavevector corresponds to the superlattice reflection observed by the experiment in the intermediate incommensurate phase between 105 K and 125 K. Therefore, the successive structural transitions of YbPd can be correctly reproduced by including this valence-lattice interaction.