Vortex creep down to 0.3 K in superconducting Fe(Te,Se) single crystals
Résumé
We report on a study of the vortex creep in Fe1+δ(TexSe1−x ) single crystals (x = 0.5 and 0.4) down to 0.28 K (∼Tc/50) and up to μ0Ha = 2T. The relaxation of the current density [J (t )] has been measured during 20 hours and the decay of J (t ) can be well described by a J (t ) ∝ [ln(t/t0)]−1/μ law.We show that the relaxation exponent μ tends towards 0 forT <2K and μ0Ha < 0.1T [i.e. J (t ) → (t0/t)α] and increases for increasing T and/or Ha . Our measurements strongly suggest that the logarithmic creep rate R = −d ln(J )/d ln(t ) remains finite at zero temperature (R|T→0 → 2%) and hence that quantum creep plays a dominant role in the relaxation process at low temperature. A maximum is observed in both the temperature and field dependence of R(t = 100s,T,Ha ), which can be associated to a crossover from a single vortex (one-dimensional) to a bundle (three-dimensional) creep regime.
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2014_Klein_PRB89_Vortex_creep_down_to_0.3_K_in_superconducting_Fe_Te_Se_single_crystals.pdf (985.77 Ko)
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