Münster 1997 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 14: Postersitzung II: Korrelierte Systeme(1-40), Theorie der Supraleitung(41-50), Metall-Isolator-Übergang, Lokalisierung(51-66), Niederdimensionale Systeme, Quantenhalleffekt(67-80), Pinning, kritische Ströme und Vortexdynamik(81-93), HTSL-Drähte und -Bänder(94-98), Massive HTSL(99-104), supraleitende Borkarbide(105-109)

TT 14.81: Poster

Mittwoch, 19. März 1997, 15:00–18:30, Z1

Phonon density of states and specific heat anomaly in K_0.3MoO₃ — •Herwig Requardt^1,2, Roland Currat¹, Pierre Monceau², and Emilio Lorenzo³ — ¹Institut Laue Langevin, BP 156, F–38042 Grenoble — ²CRTBT - CNRS, BP 166, F–38042 Grenoble — ³Lab. de Cristallographie - CNRS, BP 166, F–38042 Grenoble

In the quasi-one-dimensional (Q1D) charge-density-wave (CDW) systems (TaSe₄)₂I, K_0.3MoO₃ and KCP, an anomaly of the specific heat C_P at temperatures of several Kelvin has been observed (Lasjaunias et al.). In contrast to an earlier interpretation of these anomalies as originating from phason–like excitations of the CDW, Lorenzo et al.[1] recently related the C_P–anomaly in the case of (TaSe₄)₂I to the 1D–character of the acoustic phonon dispersion curves. To determine the origin of the C_P–anomaly in the case of K_0.3MoO₃, we performed time-of-flight neutron scattering measurements to determine the generalized phonon density of states (PDOS). At low energies the PDOS shows an excess to a Debye-law, which gives rise to the observed anomalous specific heat behavior. Based on the acoustic phonon dispersion curves measured by Pouget et al.[2] we calculated the low–energy PDOS of the system, using a simplified model. The model succeeds in reproducing the low–energy excess PDOS and establishes the phononic origin of the observed specific heat anomaly.

[1] J.E.Lorenzo et al., Phys. Rev. B 53, 8316 (1996)

[2] J.P.Pouget et al., Phys. Rev. B 43, 8421 (1991)