Andreev spectroscopy of FeSe: evidence for two-gap superconductivityстатья
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Дата последнего поиска статьи во внешних источниках: 20 сентября 2013 г.
Аннотация:Current-voltage characteristics of Andreev superconductor-constriction-superconductor (ScS) contacts in polycrystalline samples of FeSe with critical temperature Tc = (12 ± 1) K have been measured using a break-junction technique. In Sharvin- type nanocontacts two sets of subharmonic gap structures were detected due to multiple Andreev reflections indicating the existence of two nodeless superconducting gaps: Δ_Large = (2.75 ± 0.3) meV and Δ_Small = (0.8 ± 0.2) meV. Well-shaped current-voltage characteristics (CVCs) for stacks of Andreev contacts with the number of contacts up to five were observed due to the layered structure of FeSe (intrinsic multiple Andreev reflections effect). An additional fine structure in the CVCs of Andreev ScS nanocontacts is attributed to the existence of a Leggett mode. A linear relation between the superconducting gap Δ_Large and the magnetic resonance energy E_magn_res ≈ 2Δ_Large is found to be valid for layered iron pnictides.