Abstract
We report on the experimental observation of the proximity induced superconductivity in an indium gallium arsenide (In0.75Ga0.25As) quantum well. The Josephson junction was fabricated by several photo-lithographic processes on an InGaAs heterojunction and Niobium (Nb) was used as superconducting electrodes. Owing to the Andreev reflections and Andreev bound states at the Nb-In0.75Ga0.25As quantum well-Nb interfaces, the subharmonic energy gap structures (SGS) are observed at the differential conductance (dI/dV) versus voltage (V) plots when the applied source-drain bias voltages satisfy the expression VSD = 2Δ/ne. The dI/dV as a function of applied magnetic field B shows a maximum at zero B which decreases by increasing B. When decreasing B to below ±0.4 T, a hysteresis and shift of the conductance maxima close to B = 0 T are observed. Our results help to pave the way to the development of integrated coherent quantum circuitry.
Highlights
The proximity effect in hybrid superconductor-semiconductor (S-Sm) structures, e.g. superconducting correlations and supercurrent transport in a semiconductor connected to a superconductor mediated by phase coherent Andreev reflections [1,2,3], provides the possibility to study some fascinating fundamental physics such as Kondo-enhanced Andreev tunnelling [4], supercurrent reversal in quantum dots [5], Josephson quantum electron pumps [6]
Here we present our experimental results on proximity induced superconductivity in a high-mobility twodimensional electron gas (2DEG) in an indium gallium arsenide (In0.75Ga0.25As) heterostructure
The false color Scanning Electron Micrograph (SEM) image of the planar Nb-In0.75Ga0.25As-Nb Josephson junction is shown in the inset of Fig. 1
Summary
The proximity effect in hybrid superconductor-semiconductor (S-Sm) structures, e.g. superconducting correlations and supercurrent transport in a semiconductor connected to a superconductor mediated by phase coherent Andreev reflections [1,2,3], provides the possibility to study some fascinating fundamental physics such as Kondo-enhanced Andreev tunnelling [4], supercurrent reversal in quantum dots [5], Josephson quantum electron pumps [6]. Andreev reflections and bound states due to the electron and hole like quasiparticle correlations at the Nb-In0.75Ga0.25As quantum well interfaces lead to the observation of a U-shape dip at low-bias voltage of the differential resistance dV/dI (VSD) plot, as well as the subharmonic energy gap structures (SGS) at V = 2D/ne where the D is Nb superconducting gap Both the induced gap and SGS features suppress significantly as temperature T and magnetic field B are applied to the system – due to the T and B dependences of DNb – leading to a shift of the SGS toward zero bias [11].
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