Dresden 2009 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 9: Poster 1
HL 9.118: Poster
Monday, March 23, 2009, 14:30–17:00, P2
Coulomb blockade dominates transport across lateral (001)-(Ga,Mn)As nanoconstrictions — •Markus Schlapps1, Teresa Lermer1, Stefan Geißler1, Daniel Neumaier1, Rashid Gareev1, Janusz Sadowski2, Werner Wegscheider1, and Dieter Weiss1 — 1Universität Regensburg — 2Max-Lab, Lund University, Sweden
Narrow constrictions in GaMnAs films display large magnetoresistance (MR) effects [1-6]. Explanations of these effects involve the formation of a tunneling barrier [1,2]. A pronounced dependence of the resistance on the magnetization direction was ascribed to the tunneling anisotropic MR [2] and, more recently, to a metal-insulator transition [4,5]. On the other hand, experiments on a narrow GaMnAs channel revealed a Coulomb blockade anisotropic MR effect[6]. Hence the microscopic origin of the huge MR effects is still under discussion. Here we present experiments on single-constricted GaMnAs wires. Based on measurements of the resistances' bias voltage and temperature dependence down to millikelvin temperatures we compare the models currently used. We show that the large MR jumps of up to several thousand percent are solely connected to the magnetization alignment in the constriction and that the transport mechanism is dominated by Coulomb blockade. Using additional side-gates the device acts as a single electron transistor. [1] C. Ruester et al. , PRL 91, 216602 (2003) [2] A. D. Giddings et al. , PRL 94, 127202 (2005) [3] M. Schlapps et al. , phys. stat. sol. (a) 203, No. 14, 3597 (2006) [4] M. Ciorga et al. , New J. Phys. 9, 351 (2007) [5] K. Pappert et al. , Nature Physics 3, 573 - 578 (2007) [6] J. Wunderlich et al. , PRL 97, 077201 (2006)