Hamiltonian approach to the transport properties of superconducting quantum point contacts
- Departamento de Fisica Teorica de la Materia Condensada C-V, Facultad de Ciencias, Universidad Autonoma de Madrid, E-28049 Madrid (Spain)
A microscopic theory of the transport properties of quantum point contacts giving a unified description of the normal conductor-superconductor ({ital N}-{ital S}) and superconductor-superconductor ({ital S}-{ital S}) cases is presented. It is based on a model Hamiltonian describing charge transfer processes in the contact region and makes use of nonequilibrium Green function techniques for the calculation of the relevant quantities. It is explicitly shown that when calculations are performed up to infinite order in the coupling between the electrodes, the theory contains all known results predicted by the more usual scattering approach for {ital N}-{ital S} and {ital S}-{ital S} contacts. For the latter we introduce a specific formulation for dealing with the nonstationary transport properties. An efficient algorithm is developed for obtaining the dc and ac current components, which allows a detailed analysis of the different current-voltage characteristics for all range of parameters. We finally address the less understood small bias limit, for which some analytical results can be obtained within the present formalism. It is shown that four different physical regimes can be reached in this limit depending on the values of the inelastic scattering rate and the contact transmission. The behavior of the system in these regimes is discussed together with the conditions for their experimental observability. {copyright} {ital 1996 The American Physical Society.}
- OSTI ID:
- 383183
- Journal Information:
- Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 10 Vol. 54; ISSN 0163-1829; ISSN PRBMDO
- Country of Publication:
- United States
- Language:
- English
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