Ref HAL: hal-00541604_v1
DOI: 10.1103/PhysRevB.75.153310
WoS: 000246075300020
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1 Citation
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Spin-orbit interaction in a quantum dot couples far-infrared radiation to noncenter-of-mass excitation modes, even for parabolic confinement and dipole approximation. The intensities of the absorption peaks satisfy the optical sum rule, giving direct information on the total number of electrons inside the dot. In the case of a circularly polarized radiation, the sum rule is insensitive to the strength of a Rashba spin-orbit coupling due to an electric field orthogonal to the dot plane, but not to other sources of spin-orbit interaction, thus allowing one to discriminate between the two.

Ref HAL: hal-00541606_v1
DOI: 10.1103/PhysRevB.76.161302
WoS: 000250620600008
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5 Citations
Résumé:

We use the resistance fluctuations (RFs) appearing in the integer quantum Hall regime to scan the density of states of a very thin Hall bar. By applying a dc voltage on a top gate, we analyze the correlation properties of the various resistances as a function of the magnetic field and the carrier density. In the gate voltage-magnetic field plane, these RFs follow lines with slopes quantized in unit of filling factor and the slope of these RFs depends on their correlation properties.

Ref HAL: hal-00394196_v1
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Ref HAL: hal-00394194_v1
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Ref HAL: hal-03037691_v1
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We present a low temperature magnetoconductance study of a submicron hall bar made from an AlGaAs/InGaAs/GaAs heterostructure. Experiments were performed at very low temperature (120 mK), with a magnetic field ranging from OT to 13.5 T. In the presence of a quantizing magnetic field, at the transition between two quantized Hall plateaus, a succession of sharp peaks is detected in the Hall signal RH and in the longitudinal resistance R-L. The peaks appearing on the high-v side of the R-L transition appear to be different from the peaks appearing on the low-v side. They mainly differ by their temperature dependence. On the high-v side of the RL transition, the temperature evolution of the peaks is typical for resonant tunneling through a single state in one of the antidots that are progressively formed when the initially occupied LL is emptied. On the low v of the transition, by contrast, the temperature dependence is different. This may be related to the asymmetry of the density of states, or to additional inelastic processes.

Commentaires: 28th International Conference on the Physics of Semiconductors (ICPS-28), Vienna, AUSTRIA, JUL 24-28, 2006

Ref HAL: hal-00541617_v1
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Resonant tunnelling via single impurities placed in a single barrier was experimentally studied. The typically observed structures in the current-voltage characteristics seem to be paired. Such a pair can be interpreted as ground and excited states of an impurity, related to X-xy and X-z valleys, which is in agreement with the results obtained for big mesas. However, it is not clear why X-xy states can be seen without any phonon participation.

Ref HAL: hal-00541608_v1
DOI: 10.1103/PhysRevB.73.155415
WoS: 000237155100102
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9 Citations
Résumé:

A single impurity is used to probe the local density of states of a two-dimensional electron gas (2DEG) in a resonant tunneling experiment. The studies have been performed in the GaAs/AlAs/GaAs system, with Si donors incorporated into the AlAs layer, on submicrometer junctions. The current-voltage characteristics clearly show peaks corresponding to the formation of Landau levels. Moreover, additional fine-structure superimposed on the Landau levels are resolved. Detailed magnetic field studies suggest that those peaks reflect the single particle states of the Landau levels. The surprisingly rapid shift of these additional features in a magnetic field is reproduced in a model, which takes into account disorder in the plane of the 2DEG.