Regensburg 2007 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 52: Transport properties

HL 52.2: Talk

Friday, March 30, 2007, 11:15–11:30, H14

Carrier-carrier interaction in 2D and 1D ferromagnetic (Ga,Mn)As — •Daniel Neumaier, Konrad Wagner, Stefan Geißler, Ursula Wurstbauer, Janosch Sadowski, Matthias Reinwald, Werner Wegscheider, and Dieter Weiss — Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Regensburg, Germany

We investigated the temperature dependency of conductance G of ferromagnetic (Ga,Mn)As mesoscopic wires and films (Tc~100K) below 1K. The quasi two dimensional samples have a width of 10μm and a length of 60μm, while the quasi one dimensional samples have a width of only 40nm and a length of 7,5μm. The thickness was in both cases between 20nm and 50nm, smaller than the phase coherence length and thermal diffusion length at low T. At low temperatures the conductance of the (Ga,Mn)As samples decreases with decreasing temperature, often ascribed to the Kondo effect. This temperature dependency of G is independent of an externally applied magnetic field in a wide temperature range. A weak localization contribution was only found in some samples below 50mK. By comparing the temperature dependency of the conductance of quasi 2D samples with quasi 1D samples and by applying an external magnetic field, we show that the conductance's temperature dependence can be explained well in terms of enhanced electron-electron interaction, displaying universal behaviour.