Dresden 2003 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 18: Metall-Isolator-Überg
änge in Quantensystemen I

TT 18.10: Hauptvortrag

Donnerstag, 27. März 2003, 17:00–17:30, HSZ304

Graphite as a Highly Correlated Electron System — •Yakov Kopelevich — Instituto de Fisica, Universidade Estadual de Campinas, Unicamp 13083-970, Campinas, Sao Paulo, Brasil

Although a considerable amount of the research work has been done on graphite, its physical properties are still not well understood. In the present talk we review recent observations of magnetic-field-driven metal-insulator and insulator-metal transitions (MIT and IMT), quantum Hall effect (QHE), superconducting and ferromagnetic correlations, and magnetic-field-dependent g-factor in graphite. In particular, the experimental results provide evidence that the low field (∼ 1 kOe) MIT is associated with the transition between Bose metal and excitonic insulator states. However, the reentrant IMT which takes place with the field increase can consistently be understood assuming the occurrence of superconducting correlations due to Landau level quantization. We argue that the QHE, observed only for strongly anisotropic quasi-two-dimensional (2D) graphite samples, and superconducting correlations can represent the same phenomenon, i.e. Cooper pairs in the quasi-2D samples can form a highly correlated Boson liquid.