Quasiparticle energy relaxation in the cuprate superconductors

Abstract

At high flux-flow velocities in the mixed state of a type-II superconductor the nonequilibrium distribution of the quasiparticles is shifted to higher energies. As shown theoretically by Larkin and Ovchinnikov, a distinct signature of this nonequilibrium effect is an electronic instability, resulting in a sharp kink in the current-voltage characteristic at a critical vortex velocity vφ*. From measurements of vφ* the quasiparticle-energy relaxation rate τɛ−1 can be found. We have measured this instability point for epitaxial c axis oriented films of La1.85Sr0.15CuO4−x and YBa2Cu3O7−δ. In both cuprates the observed temperature dependence of τɛ−1 could be well fitted with the function τɛ−1=aexp[−2Δ(T)/kBT], suggesting that the electron-electron recombination process, perhaps in combination with the emission of another excitation, is crucial. As an example of a low-Tc superconductor we have also studied amorphous Mo3Si films and found that τɛ−1 can be fitted by a function similar to that we have used for the cuprates, again indicating the importance of the electron-electron interaction.

Source-reported materials — not catalogue approval

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