Berlin 2008 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 30: Quantum dots and wires: Transport properties II

HL 30.2: Vortrag

Dienstag, 26. Februar 2008, 14:30–14:45, ER 164

Coherent Spin Rotations in Double Quantum Dots — •Rafael Sanchez, Carlos Lopez-monis, and Gloria Platero — Instituto de Ciencia de Materiales, CSIC, Madrid 28049, Spain

We analyze coherent spin rotations in a DC biased double quantum dot driven by crossed DC and AC magnetic fields. In this configuration, spatial delocalization due to inter-dot tunneling competes with intra-dot spin rotations induced by the time dependent magnetic field, giving rise to a complicated time dependent behavior of the tunnelling current which strongly depends on the ratio between the different Rabi frequencies involved. When the Zeeman splitting has the same value in both dots and spin flip is negligible, the electrons remain in the triplet subspace performing coherent spin rotations and current does not flow. This electronic trapping is removed either by finite spin relaxation or when the Zeeman splitting is different in each quantum dot. In the last case, we will show that applying a resonant bi-chromatic magnetic field, the electrons become trapped in a coherent superposition of states and electronic transport is blocked. Then, manipulating AC magnetic fields allows to drive electrons to perform coherent spin rotations which can be unambiguously detected by direct measurement of the tunnelling current.