Regensburg 2010 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 46: Quantum Dots and Wires: Transport
HL 46.13: Talk
Wednesday, March 24, 2010, 17:15–17:30, H17
Aharonov-Bohm phase shift in an asymmetric quantum ring — •S.S. Buchholz1, S.F. Fischer1, U. Kunze1, D. Reuter2, and A.D. Wieck2 — 1Werkstoffe und Nanoelektronik, Ruhr-Universität Bochum — 2Angewandte Festkörperphysik, Ruhr-Universität Bochum
The phase evolution of the electron wave function can be used to study fundamental interaction effects in quantum coherent transport. Therefore, we investigate a multi-terminal quantum ring which allows phase shift measurements in Aharonov-Bohm (AB) experiments. We focus on non-local measurements in an asymmetric four-terminal electron wave guide geometry [1].
The device was fabricated from a GaAs/AlGaAs heterostructure and is covered with a global Au gate. The quantum ring is linked to two-dimensional reservoirs via quantum wire leads. Transport measurements were performed at 23 mK with lock-in technique. AB resistance oscillations prove coherence in two- and four-terminal probe configurations [1] and obey time reversal symmetry: Two-probe measurements show phase rigidity. The ring’s asymmetry allows modulating the phase of the interference pattern electrostatically: Via the gate voltage we can tune the electrons’ Fermi wavelength along the unequally long paths and observe a gradual phase shift in the non-local measurement configuration. Numerical results from a time-dependent wave packet approach (see contribution by Ch. Kreisbeck) qualitatively reproduce our results in phase shift, phase jumps and the observation of higher harmonics.
[1] S.S. Buchholz et al., Appl. Phys. Lett. 94, 022107 (2009).