# Dresden 2014 – wissenschaftliches Programm

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# HL: Fachverband Halbleiterphysik

## HL 16: Electron spin qubits in semiconductor quantum dots (Focus session with TT)

### HL 16.10: Vortrag

### Montag, 31. März 2014, 18:15–18:30, POT 051

**Spin-orbit effects on nuclear state preparation at the ***S*−*T*_{+}** anti-crossing in double quantum dots** — •Marko J. Rančić and Guido Burkard — University of Konstanz

We explore the interplay of spin-orbit and hyperfine effects on the nuclear preparation schemes in two-electron double quantum dots, e.g. in GaAs.
The quantity of utmost interest is the electron spin decoherence time *T*_{2}^{*} in dependence of the number of sweeps through the electron spin singlet *S* triplet *T*_{+} anti-crossing.
Decoherence of the electron spin is caused by the difference field induced by the nuclear spins.
We study the case where a singlet *S*(2,0) is initialized, in which both electrons are in the left dot. Subsequently,
the system is driven repeatedly through the anti-crossing and back using linear electrical bias sweeps.
Our model describes the passage through the anti-crossing with a large number of equally spaced, step-like parameter increments.
We develop a numerical method describing the nuclear spins fully quantum mechanically, which allows us to track their dynamics.
Both Rashba and Dresselhaus spin-orbit terms do depend on the angle θ between the [110] crystallographic and the inter-dot axis.
Our results show that the suppression of decoherence (and therefore the enhancement of *T*_{2}^{*}) is inversely proportional to the strength of the spin-orbit interaction, which
is tuned by varying the angle θ.