ar X iv : c on d - m at / 9 51 20 31 v 1 5 D ec 1 99 5 Thermal noise in superconducting quantum point - contacts
نویسندگان
چکیده
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 quasi-ballistic 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. Present technologies make it possible to fabricate superconducting point-contacts in the nanometer scale. Examples of these kind of systems are the recently developed atomic size break-junctions [1] and the split-gate superconductor-two-dimensional electron gas-su-perconductor junction of Takayanagi et al. [2]. In both cases the electronic transport takes
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