The seemingly simple question, but nobody can answer it unambiguously.
Experimental setup to the question is shown in Figure 1 in
Preprint Tuning of Lifetime of Cooper pairs in a Massive Aluminum Ring
A persistent supercurrent flows in a SC aluminum ring. Then we connect the SC aluminum ring to an aluminum wire, the second end of the wire is in a separate chamber with T > Tc (or H > Hc) and is not SC. The temperature of the SC ring is stable below Tc. Thus the SC ring is electrically connected to a non-SC zone where electron pairs dissipate their supercurrent momenta on atom lattice. Will the remote non-SC zone suppress the persistent supercurrent in the SC ring?
The answer may be very informative. Electron pairs drift between connected SC and non-SC zones. The pair density in the SC zone is not zero, in the non-SC zone — zero. Hence the pairs annihilate and arise. So paired electrons in the SC ring are not permanently paired and become single for a while. Thus, if the supercurrent decays, it is a consequence of the non-permanency of pairs. In other words, the supercurrent is eternal if its pairs are permanent (what is the case when the SC and non-SC zones are disconnected).
Hi Dear Prof. Stanislav Dolgopolov
I guess that the mechanism that you ask is the inverse of Andreev Reflection, isn't it?
Of course you talk about an specific geometry "a ring", that part I dont know.
KInd Regards.
Hello Dear Professor Contreras.
I don't specify the mechanism of pair drift and recombination. But I can assert that pairs inside a persistent current can be replaced with newly created pairs, which initially didn't participate in the current. It is easy to show: the pair density in the SC ring is constant, and a fraction of pairs drifts into non-SC area, where the pair density is zero. Hence, in the non-SC area, incoming pairs annihilate, and newly created pairs somehow restore the pair density in the SC ring.
Hi Dear Prof. Stanislav Dolgopolov
Thank you for the answer & well it seems to be logical, but you do specify the mechanism implicitly, when you write the statement "the created pairs, which initially didn't participate in the current", because you are saying that new pairs of supercurrent bosons are created somehow. They are created, and there is a superconducting mechanism for their creation, even we do not know which one is, if BCS or another unknown one.
Kind Regards.
Dear Professor Guynn,
Thank you for the link. I think also, BCS is not able to explain the Meissner effect. And the experiment proposed can clarify another prediction of the BCS theory. If the persistent supercurrent decays due to the remote non-SC zone, then a necessary condition for the supercurrent is permanency (non-breaking) of electron pairs. BCS predicts, that SC pairs can annihilate/arise.
Dear Professor Contreras,
Thank you for the note. You are right - the pair creation mechanism is a special story. Now I want only to examine a BCS prediction that the SC pairs can be created/annihilated inside a supercurrent. If the persistent supercurrent decays due to the remote non-SC zone, then a necessary condition for the supercurrent is permanency (non-breaking) of pairs and then the SC pairs don’t annihilate/arise.
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