We report on single electron transport via a novel quantum dot structure fabricated by a combination of mesa etching and gate formation. In this device electrons are confined in an etched submicron wire and squeezed further by two barrier gates. The resulting dot is of a very small size, and the number of confined electrons can be tuned down to the few electron limit. This novel structure has a large charging energy and an improved current quantization during turnstile operation. In small dots, containing only a few electrons, we found Coulomb oscillations with an unexplained multiple peak structure.
Electrical-transport properties of mesoscopic junctions consisting of a ballistic two-dimensional electron gas coupled at two sides to overlaying superconducting contacts are presented. The properties suggest that, despite the presence of transport limiting barriers in the sample, supercurrents are carried by a few modes that have near-unity transmission probability. We can qualitatively account for the presence of these resonances by the theory of disorder-induced opening of tunnel channels. ͓S0163-1829͑96͒51028-3͔Over the past few years, transport properties of phasecoherent normal ͑N͒ conductors coupled to superconducting ͑S͒ electrodes have received considerable interest. In such structures the interaction between the superconducting condensate and a normal electron gas can be studied on a mesoscopic scale. The process responsible for this interaction is Andreev reflection: an electron incident from N on a N-S interface can be backscattered as a hole, which has the phase of the incident electron shifted by an amount depending on energy and the macroscopic phase of S. As a result of this scattering process transport properties of such hybrid structures can change drastically.
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Related contentAharonov-Bohm rings with strong spin-orbit interaction: the role of samplespecific properties F Nichele, Y Komijani, S Hennel et al. Abstract. The magnetoresistance of a quasi-ballistic Aharonov-Bohm (AB) ring defined in the two-dimensional electron gas (2DEG) of an InP/In 0.8 Ga 0.2 As quantum well is studied. The ring is connected to an Al contact on one side and to a 2DEG reservoir at the other side. Two distinct magnetic field regimes can be identified. At magnetic field values where time-reversal symmetry (TRS) is broken, AB oscillations are observed. Besides oscillations with h/e periodicity, we also observe higher harmonics with h/2e and h/3e periods. In the lowmagnetic field range, where TRS is preserved, the AB oscillations are alternately dominated by the h/e or h/2e component, depending on the bias voltage. Although Al is superconducting at these low magnetic fields, no evidence is found that the observed AB oscillations are related to the proximity of the superconductor. The bias voltage dependence is qualitatively described in terms of a 1D scattering model.
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