Evidence for long-lived quasiparticles trapped in superconducting point contacts

M. Zgirski (1) , L. Bretheau (1) , Q. Le Masne (1) , Hugues Pothier (1) , Daniel Esteve (1) , C. Urbina (1)

1 QUANTRONICS - Quantronics Group

We have observed that the supercurrent across phase-biased, highly transmitting atomic size contacts is strongly reduced within a broad phase interval around π. We attribute this effect to quasiparticle trapping in one of the discrete sub-gap Andreev bound states formed at the contact. Trapping occurs essentially when the Andreev energy is smaller than half the superconducting gap Δ, a situation in which the lifetime of trapped quasiparticles is found to exceed 100 μs. The origin of this sharp energy threshold is presently not understood.

Mots clés: Andreev states; quasiparticle poisoning; atomic contact; quantum point contact; quasiparticle lifetime

Domaines: Systèmes mésoscopiques et effet Hall quantique [cond-mat.mes-hall]; Supraconductivité [cond-mat.supr-con]

M. Zgirski, L. Bretheau, Q. Le Masne, Hugues Pothier, Daniel Esteve, et al.. Evidence for long-lived quasiparticles trapped in superconducting point contacts. Physical Review Letters, 2011, 106 (257003), pp.257003-1. ⟨10.1103/PhysRevLett.106.257003⟩. ⟨hal-00595339⟩