Magneto-Transport and Electronic Phase Transition in Graphite in High Magnetic Fields

Abstract

Electronic states in solids under extremely high magnetic fields are of great interest in relation to a phase transition such as the Wigner crystallization and the charge density wave (CDW) transition [l]. An anomaly recently discovered in the magnetoresistance in single crystal graphite in high magnetic fields at low temperatures [2] appears to be one of such phase transitions [3, 4]. In an earlier paper [4], we have investigated in detail the amount of the change of the magnetoresistance at the anomaly in pulsed high magnetic fields. Typical examples of the experimental recordings of the magnetoresistance ρ is shown in Fig. 1 for two different samples. For D.C. current, the magnetoresistance once saturates around 12 T, and decreases with increasing field up to a critical field of the anomaly. At the critical field, 31 T in this case, the magnetoresistance abruptly starts to increase. This is the anomaly of the present interest. In some samples, the P-H curve showed just a flat part between about 12 T and the anomaly point, without a decrease of ρ before the anomaly. As the critical field for the anomaly to occur depends on temperature, Yoshioka and Fukuyama proposed a model to explain this anomaly on the basis of the charge density wave (CDW) formed in a quasi-one-dimen- sional Landau subband in an extreme quantum limit [5].