Berlin 2012 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 20: Focus Session: Magnetic Semiconductors (jointly with MA)

HL 20.4: Talk

Monday, March 26, 2012, 17:15–17:30, EW 202

Effects of disorder and hole tunneling transport on the ferromagnetism in GaMnAs quantum wells — •Christian Ertler and Walter Pötz — Institute of Physics, Karl-Franzens University Graz, Universitätsplatz 5, 8010 Graz, Austria

Recent experiments on heterostructures comprising GaMnAs quantum wells [1] evoke strong debates about the nearly absence of ferromagnetic order observed in these structures. Based on a tight-binding approach and the non-equilibrium Green's function formalism we investigate self-consistently the interplay between ferromagnetic order, structural defects, and hole tunnel current [2]. We find that disorder has a strong influence on the IV characteristic in efficiently washing out negative differential conductance as found in experiment [1]. The hole density in the well is established by tunneling from the p-doped GaAs leads, resulting in small exchange splittings in the well on the order of 10 meV for reasonable lead doping. We predict that for cleaner samples the ferromagnetic order in the well tends to be destroyed under resonance condition. This effect leads to a characteristic signature in the spin-polarization of the tunnel current available to experimental detection.

[1] S. Ohya, K. Takata and M. Tanaka, "Nearly non-magnetic valence band of the ferromagnetic semiconductor GaMnAs", Nature Physics, 7, 342 (2011).

[2] C. Ertler and W. Pötz, "Electrical control of ferromagnetism and bias anomaly in Mn-doped semiconductor heterostructures", Phys. Rev. B 84, 165309 (2011).