Low-frequency excitations in incommensurate biphenyl as studied by very low-temperature specific heat
Groupe Matière Condensée et Matériaux, UMR au CNRS 804, Université de Rennes 1,
35042 Rennes cedex, France
2 Centre de Recherches sur les Très Basses Températures, CNRS, 38042 Grenoble cedex, France
Accepted: 7 April 1997
We present the first specific-heat data of biphenyl in the temperature range from 70 mK to 7.3 K. The extra phononic contribution is principally attributed to the propagating phason branch in agreement with neutron data. From these measurements, one can estimate a relatively large weight of this branch confirming its anisotropic dispersion with weak velocities. The shifting of the modulation boundaries in the metastable incommensurate phase III can generate low-energy excitation contribution. Contrary to the case of disordered crystals, no aging effects in the energy relaxation and quasi-linear T term were detected.
PACS: 65.40.+g – Heat capacities of solids / 64.70.Rh – Commensurate-incommensurate transitions / 63.20.Dj – Phonon states and bands, normal modes, and phonon dispersion
© EDP Sciences, 1997