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Doubled full shot noise in quantum coherent superconductor-semiconductor junctions.
F Lefloch1, C Hoffmann, M Sanquer
1Département de Recherche Fondamentale sur la Matière Condensée/SPSMS, CEA Grenoble, 17 avenue des Martyrs, 38054 Grenoble Cedex 09, France.
Physical Review Letters
|March 14, 2003
Summary
We studied shot noise in superconductor-normal metal junctions. Coherent Andreev reflections cause noise twice the Poisson level, which shifts to normal levels as quasiparticles dominate.
Area of Science:
- Condensed matter physics
- Superconductivity
- Mesoscopic physics
Background:
- Understanding charge transport in superconductor-normal metal junctions is crucial for quantum device applications.
- Disordered normal metals introduce unique quantum phenomena in hybrid structures.
Purpose of the Study:
- Investigate low-temperature shot noise in superconductor (TiN) - strongly disordered normal metal (Si) junctions.
- Characterize the influence of coherent multiple Andreev reflections and quasiparticle contributions on noise.
Main Methods:
- Performed low-temperature shot noise measurements.
- Analyzed conductance and noise characteristics across varying voltages.
Main Results:
- Observed a conductance maximum at low energy attributed to coherent multiple Andreev reflections.
- Shot noise was found to be twice the Poisson level (S = 4eI) under these conditions.
- At higher voltages, subgap conductance minimum correlated with a transition to normal shot noise (S = 2eI) due to quasiparticles.
Conclusions:
- Coherent multiple Andreev reflections significantly enhance shot noise in superconductor-normal metal junctions.
- Quasiparticle scattering provides a contrasting contribution to noise at higher energies.
- These findings offer insights into quantum transport mechanisms in disordered hybrid systems.