Published on January 11, 2008
Analogy between pinned mode in charge density glass and Boson peak in glassesKatica Biljaković1, Jean-Claude Lasjaunias2, Damir Starešinić11Institut of Physics, Zagreb, Croatia2CRTBT-CNRS, Grenoble, France: Analogy between pinned mode in charge density glass and Boson peak in glasses Katica Biljaković1, Jean-Claude Lasjaunias2, Damir Starešinić1 1Institut of Physics, Zagreb, Croatia 2CRTBT-CNRS, Grenoble, France Shematic plot of dielectric response of two types of glasses (taken from ref. 4) with type A, or strong one and type B, as fragile one; (or structural) relaxation presents viscosity (yellow), relaxation or Johari-Goldstein process (blue), fast proces as cage effect (red), boson peak (pink), intramolecular modes (gray). “strong glass” character: - low frequency wing commes out from the pinning resonance and freezes out below 25 K - less pronounced secondary, -process, appears at the high frequency wing of the primary relaxation. low frequency wing - primary relaxation Pinning resonance Phason scattering (vphason 105 m/s) on LR domains xLR1 mm resonance at ~100 GHz Phason screening screening increases propagating velocity (and resonant frequency) Gap in phason dispersion (3<0<300 GHz ) can explain Cp at low-T J. Odin et al, EPJB 2001 Boson peak - acoustic-like excitations - THz range - nm SRO domains - sound velocity 103 m/s - peak in Cp/T3 Pinning resonance - acoustic-like excitations - GHz range - mm LR domains - phason velocity >105 m/s - may give a peak in Cp/T3 a process - relaxation of cooperative domains - crossover in GHz range …. freezes at Tg b process - remains below Tg - microscopic origin unknown b process - remains below Tg - cooperative relaxation of topological defects background loss - presumably present in all glasses - microscopic origin unknown b0 process - DW topological defects - can provide CLEE contribution - quatum decay of the pinned mode? comparison conventional glasses / DW glasses a process - relaxation of coupled LR domains - crossover in MHz range - criterion: less than 1 e in LR domain K. Biljaković et al., PRB43 3117 (1991) S. Ravy et al., PRB 69, 115113 (2004) K. Carneiro et al., PRB 13, 4258 (1976) Secondary process Overall complexity of the manifestation of the CDW glass points to a new class of glass. Relevant degrees of freedom concern the CDW superstructure on characteristic scales of the size of the phase coherence length (l~m). As the lattice distortion associated with the CDW can be thought of as being a “frozen” phonon, we discuss its possible manifestations in relation with phenomenology of boson peak (BP) in glasses. "Low-frequency" dielectric response of blue bronze K0.3MoO3 Possible phason contribution with two cutoffs: 0=17 GHz and =100 GHz NbSe3 (TMTSF)AsF6 BP in neutron scattering BP in Raman scattering BP in Cp and thermal conductivity x=h/kBT T0= h0/kB and phason Debye T Ioffe-Regle criterion for ill defined phonons or crossover from weak to strong scattering acac works also for phasons?!