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Abstract: We study small oscillations of the order parameter in weakly and stronglypaired superconductors driven slightly out of equilibrium, in the collisionlessapproximation. While it was known for quite some time that the amplitude of theoscillations in a weakly paired superconductor decays as 1-t^1-2, we showthat in a superconductor sufficiently strongly paired so that its fermions formbound states usually referred to as molecules, these oscillations decay as1-t^3-2. The transition between these two regimes happens when the chemicalpotential of the superconductor vanishes, thus the behavior of the oscillationscan be used to distinguish weakly and strongly paired superconductors. Theseresults are obtained in the mean field approximation which may not be reliablein the crossover region between the strong and weak pairing, so we also obtainidentical results within the two-channel model, which can be tuned to bereliable throughout the entire crossover, although it then describes a specialtype of interactions between the fermions which may be difficult to observeexperimentally. Finally, we interpret the result in the strongly pairedsuperconductor as the probability of the molecular decay as a function of time.



Autor: V. Gurarie

Fuente: https://arxiv.org/







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