Regensburg 2010 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 63: III-V Semiconductors

HL 63.5: Talk

Friday, March 26, 2010, 11:15–11:30, H13

Engineering ultralong spin coherence in 2D hole systems at sub-Kelvin temperatures — •Kugler Michael, Korn Tobias, Griesbeck Michael, Schulz Robert, Hirmer Marika, Schuh Dieter, Wegscheider Werner, and Schüller Christian — Institut für Experimentelle und Angewandte Physik, Universität Regensburg

For the realisation of scalable solid-state quantum-bit systems, spins in semiconductor quantum dots are promising candidates. A key requirement is a sufficiently long coherence time of the spin system. Recently, hole spins in III-V-based quantum dots were discussed as alternatives to electron spins, since the hole spin is not affected by contact hyperfine interaction with the nuclear spins.

Here, we report a breakthrough in the spin coherence times of hole ensembles, confined in so called natural quantum dots, in narrow GaAs/AlGaAs quantum wells at sub-Kelvin temperatures. Consistently, time-resolved Faraday rotation and resonant spin amplification techniques deliver hole-spin coherence times, which approach in the low magnetic field limit values above 70 ns. The optical initialisation of the hole spin polarisation, as well as the interconnected electron and hole spin dynamics in our samples are well reproduced using a rate equation model [1].

Furthermore, electric control of the hole g factor could be achieved via application of a gate voltage, resulting in a shift of more than 50 % in the value of the g factor [2].

[1] Korn et al., cond-mat0909.3711v2, submitted.

[2] M. Kugler et al., Phys. Rev. B 80, 035325 (2009).