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ЖЭТФ, Том 140, Вып. 3, стр. 527 (Сентябрь 2011)
(Английский перевод - JETP, Vol. 113, No 3, p. 459, September 2011 доступен on-line на www.springer.com )

ANDREEV SPECTROSCOPY OF FeSe: EVIDENCE FOR TWO-GAP SUPERCONDUCTIVITY
Ponomarev Ya.G., Kuzmichev S.A., Mikheev M.G., Sudakova M.V., Tchesnokov S.N., Shanygina T.E., Volkova O.S., Vasiliev A.N., Wolf Th.

Поступила в редакцию: 21 Декабря 2010

DJVU (183.4K) PDF (851.8K)

Current-voltage characteristics (CVCs) of Andreev superconductor-constriction-superconductor (ScS) contacts in polycrystalline samples of FeSe with the critical temperature T_C=(12\pm 1) K have been measured using the 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 \Delta_L=(2.75\pm 0.3) meV and \Delta_S=(0.8\pm 0.2) meV. Well-shaped CVCs for stacks of Andreev contacts with up to five contacts were observed due to the layered structure of FeSe (the 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 ΔL and the magnetic resonance energy E_{magres}\approx 2\Delta_L is found to be valid for layered iron pnictides.

 
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