Dresden 2011 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 63: II-VI-Compounds

HL 63.7: Vortrag

Mittwoch, 16. März 2011, 17:30–17:45, POT 151

Birefringent effect in a two dimensional electron gas — •Mathias J. Mühlbauer, Christoph Brüne, Timo Wagner, Hartmut Buhmann, and Laurens W. Molenkamp — Physikalisches Institut (EP3), Universität Würzburg, 97074 Würzburg, Germany

Rashba spin-orbit interaction is one of the most promising effects for the creation and manipulation of spin polarizations in low-dimensional electronic semiconductor systems without using external magnetic fields. In systems with strong spin orbit coupling (SOC) it should be possible to observe the electronic analogue of the birefringent effect for polarized light as proposed by M.Khodas et al. [1]. The polarization takes place at an interface between regions with different SOC. HgTe/HgCdTe quantum wells are the basis for our studies. In theses heterostructures, electron beam injection and detection can be realized by Quantum point contacts (QPC) while the SOC can be altered through gate electrodes. However, the realization of QPCs in HgTe/HgCdTe is not trivial due to the narrow band gap and the presence of the Quantum Spin Hall Effect [2]. Here, we demonstrate the possibility to fabricate QPCs using electron beam lithography and dry etching and to control its transmission with a top gate. We will present measurements of conductance and beam collimation. The conductance sequence shows steps of e^2/h suggesting that spin polarization is already taking part within the QPC. Additionaly we will show and discuss measurements on two coupled QPCs separated by a beam-splitter.

[1] M. Khodas et al.,PRL 92, 086602 (2004).

[2] M. König et al. Science, 318, 766, (2007).