Regensburg 2004 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 22: Transport im hohen Magnetfeld/Quanten-Hall-Effekt
HL 22.3: Vortrag
Dienstag, 9. März 2004, 15:45–16:00, H14
Quantum Hall Effect in Highly Oriented Pyrolytic Graphite — •Heiko Kempa1, Pablo Esquinazi1, and Yakov Kopelevich2 — 1Abteilung Supraleitung und Magnetismus, Universität Leipzig, Linnestrasse 5, D-04103 Leipzig — 2Instituto de Fisica, UNICAMP, Campinas, Sao Paulo, Brasil
Recently published work indicates the existence of the quantum Hall effect in pyrolytic graphite samples [1]. In this work we have studied this effect in detail using two different geometries: the van der Pauw electrode arrangement and the Corbino disc. Clear quantized plateaus were obtained in the Hall conductivity with the van der Pauw method. A rough estimate provides the correct value for the quantized conductivity for a single graphite layer at the plateaus within a factor of two. In the Corbino disc geometry we have measured the voltage from different electrodes positioned between the center and outer-ring electrodes. For electrodes localized at equal distances from the center electrode we have measured several well defined plateaus in agreement with those measured with the van der Pauw method. Taking into account the current penetration depth and the field dependence of the c-axis/a-axis resistivity ratio we obtain the well known absolute quantization of the plateaus, which indicates an integer quantum Hall effect. However, this “HallNo-dq-voltage in the Corbino geometry does not change sign after changing the direction of the magnetic field. We discuss our results in terms of recently published theoretical work.
[1] Y. Kopelevich et al., Phys. Rev. Lett. 90, 156402 (2003).