Soft-phonon driven hexagonal-orthorhombic phase transition in BaVS 3

Adrien Girard (1) , Michal Stekiel (1) , Wolfgang Morgenroth (1) , Bjoern Winkler (1) , Vita Ilakovac (2) , Alexei Bosak (3) , Helmuth Berger (4) , Tanaka Yoshikazu (5) , Takumi Hasegawa (6)

1 Institut für Geowissenschaften [Frankfurt am Main]
2 LCPMR - Laboratoire de Chimie Physique - Matière et Rayonnement
3 ESRF - European Synchrotron Radiation Facility
4 Institut de Physique de la Matière Complexe
5 RIKEN - RIKEN - Institute of Physical and Chemical Research [Japon]
6 Hiroshima University

The lattice dynamics of low-dimensional BaVS3 is reported accross the hexagonal-orthorhombic phase transition occuring at TS = 250 K using a combination of Thermal Diffuse Scattering of X-rays, Inelastic X-ray Scattering and DFT calculations. We observed the occurence of strongly temperature-dependent diffuse scattering upon approaching the transition, centered at the Γ points associated with weak Bragg reflections with odd L. Inelastic scattering experiment related this observation to the condensation of a low-lying overdamped optical phonon at the Brillouin zone center, evidenced by significant variations of quasi-elastic scattering. These results unravel the dynamical origin of the zigzag distortion of the V chains at TS, which is probably a prerequisite of the Peierls anomaly driving the metal-insulator transition at T MI = 70 K.

Mots clés: Structural phase transition; Phonons; Optical phonons; Research Areas; Lattice dynamics

Domaines: Physique [physics]; Matière Condensée [cond-mat]

Adrien Girard, Michal Stekiel, Wolfgang Morgenroth, Bjoern Winkler, Vita Ilakovac, et al.. Soft-phonon driven hexagonal-orthorhombic phase transition in BaVS 3. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2019, 99 (14), ⟨10.1103/PhysRevB.99.144104⟩. ⟨hal-02375879⟩