Regensburg 2004 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 20: Metall-Isolator-Überg
änge

TT 20.3: Vortrag

Mittwoch, 10. März 2004, 15:00–15:15, H18

Magnetothermal Conductivity of Highly Oriented Pyrolytic Graphite — •Konstantin Ulrich, Pablo Esquinazi, Roberto Ocaña, and Heiko Kempa — Abteilung Supraleitung und Magnetismus, Universität Leipzig, Linnestrasse 5, D-04103 Leipzig

The magnetic field (0T ≤ B ≤ 9T) dependence of the longitudinal thermal conductivity κ(T,B) of highly oriented pyrolytic graphite samples was measured in the temperature range 0.2 K ≤ T≤ 20 K for fields parallel to the c−axis. With the measured longitudinal electrical resistivity we show that the Wiedemann-Franz law is violated in the high-field (quantum-Hall) regime, where large oscillations in the thermal conductivity are measured at B > 2 T, as well as near the Metal-Insulator transition (MIT) at B ∼ 0.1 T. For a strong anisotropic graphite sample κ(B) reveals a kink-behavior at the MIT that looks similar to that predicted by the magnetic-field induced gap theory due to the phenomenon of magnetic catalysis. We discuss our results taking into account recently published models for the behavior of Dirac-like Fermi quasiparticles.