Noise and adiabatic dynamics of superconducting quantum point contacts

Athanassios Bardas, D. V. Averin

Juan Carlos Cuevas, A. Martín‐Rodero, A. Levy Yeyati

A. Martín‐Rodero, Juan Carlos Cuevas, A. Levy Yeyati +4 more

D. V. Averin

A. Martín‐Rodero, A. Levy Yeyati, Francisco José García-Vidal

We present a theory for the frequency-dependent current fluctuations in superconducting quantum point contacts (SQPC) within the dc transport regime. This theory is valid for any barrier transparency between the tunnel and ballistic limits, yielding an analytical expression for the fluctuations spectrum in the subgap region. It is shown that the level of noise in a quasiballistic SQPC may have a huge increase in comparison with the case of a normal contact carrying the same average current. The effect of this high level of noise on the actual observability of the current-phase relation for a ballistic point contact is discussed in connection with recent experimental measurements.

Dmitri A. Ivanov, M. V. Feigel’man

In a superconducting quantum point contact, dynamics of the superconducting phase is coupled to the transitions between the subgap states. We compute this coupling and derive the two-level Hamiltonian of the contact.