Regensburg 2010 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 11: Transport

HL 11.10: Vortrag

Montag, 22. März 2010, 16:30–16:45, H14

Transport Measurements on a GaAs/AlGaAs High Mobility Sample — •Lina Bockhorn¹, Werner Wegscheider², and Rolf J. Haug¹ — ¹Institut für Festkörperphysik, Leibniz Universität Hannover, Appelstr. 2, 30167 Hannover, Germany — ²ETH Zürich, Schafmattstr. 16, 8093 Zürich, Switzerland

We study the fractional Quantum-Hall effect in very high mobility two-dimensional electron systems (2DES). Hall bars are created by photolithography on a GaAs/AlGaAs quantum well containing a 2DES. The 2DES have an electron density of n_e≈2.95·10¹¹cm⁻² and a mobility of µ≈14.9·10⁶cm²/Vs at 1.5 K. Similar parameters were obtained after cooling the sample slowly to the cryostat’s base temperature (40 mK). For a given density of electrons we study the longitudinal resistance R_xx over a short range around zero magnetic field. The measurements carried out for several temperatures and different currents were applied to the Hall bar. A peak was observed at zero magnetic field for the temperature dependent measurements, as well as for the current dependent measurements. The maximum value of R_xx(B=0 T) is independent of the temperature and the applied current. The behavior of the longitudinal resistance for the temperature and the current dependent measurements is astonishing. Not only the fixed peak at the zero point is unusual, but also the distribution of the longitudinal resistance next to the peak. This region shows a different behavior for temperature variation than for different currents applied to the Hall bar. This clearly shows that the behavior for different currents is not a temperature dependent effect.