pi-Junction behavior and Andreev bound states in Kondo quantum dots with superconducting leads

We investigate the temperature- and coupling-dependent transport through Kondo dot contacts with symmetric superconducting s-wave leads. For finite temperature T we use a superconducting extension of a selfconsistent auxiliary boson scheme, termed SNCA, while at T=0 a perturbative renormalization group treatment is applied. The finite-temperature phase diagram for the 0--pi transition of the Josephson current in the junction is established and related to the phase-dependent position of the subgap Kondo resonance with respect to the Fermi energy. The conductance of the contact is evaluated in the zero-bias limit. It approaches zero in the low-temperature regime, however, at finite T its characteristics are changed through the coupling- and temperature-dependent 0--pi transition.Comment: 12 pages, 12 figure

Effect of point-contact transparency on coherent mixing of Josephson and transport supercurrents

The influence of electron reflection on dc Josephson effect in a ballistic point contact with transport current in the banks is considered theoretically. The effect of finite transparency on the vortex-like currents near the contact and at the phase difference $\phi =\pi ,$ which has been predicted recently \cite{KOSh}, is investigated. We show that at low temperatures even a small reflection on the contact destroys the mentioned vortex-like current states, which can be restored by increasing of the temperature.Comment: 6 pages, 8 Figures, Latex Fil

Josephson current between chiral superconductors

We study chiral interface Andreev bound states and their influence on the Josephson current between clean superconductors. Possible examples are superconducting Sr2RuO4 and the B-phase of the heavy-fermion superconductor UPt3. We show that, under certain conditions, the low-energy chiral surface states enhance the critical current of symmetric tunnel junctions at low temperatures. The enhancement is substantially more pronounced in quantum point contacts. In classical junctions dispersive chiral states result in a logarithmic dependence of the critical current. This logarithmic behavior contains the temperature, the barrier transparency and the broadening of the bound states, and depends on the detailed relation between these parameters. The Josephson current through the domain wall doesn't acquire this logarithmic enhancement, although the contribution from the bound states is important in this case as well.Comment: 17 pages, 6 figure