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arXiv 0906.2639cond-mat.supr-concond-mat.str-el
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不同符号序参量多带超导体中的单杂质效应

Single Impurity Effects in Multiband Superconductors with Different Sign Order Parameters

Masashige Matsumoto, Mikito Koga, Hiroaki Kusunose

摘要:

本文研究了铁磷族化合物超导体中具有不同符号序参量的多带s波超导体(+-s波超导体)的单杂质问题。不仅考虑了杂质处的带内散射,而且考虑了杂质处的带间散射。后者在杂质附近产生杂质诱导的局域束缚态。我们给出了局域束缚态能量随两种杂质散射强度变化的精确形式。杂质的基本作用在有限数量的杂质中是不变的。对单个杂质问题的主要结论有助于我们理解致密杂质在+-s波超导体中的作用。还研究了单个杂质周围的局域态密度。我们建议用杂质位核磁共振作为探测+-s波态所特有的局域束缚态的合适实验。我们发现+-s波模型被映射为手征的dx ~ 2-y ~ 2 +-idxy波,反映了反符号序参量的非常规性质.对于量子磁性杂质,带间散射使近藤单线态不稳定。

英文摘要:

A single impurity problem is investigated for multiband s-wave superconductors with different sign order parameters (+-s-wave superconductors) suggested in Fe-pnictide superconductors. Not only intraband but also interband scattering is considered at the impurity. The latter gives rise to impurity-induced local boundstates close to the impurity. We present an exact form of the energy of the local boundstates as a function of strength of the two types of impurity scattering. The essential role of the impurity is unchanged in finite number of impurities. The main conclusions for a single impurity problem help us understand effects of dense impurities in the +-s-wave superconductors. Local density of states around the single impurity is also investigated. We suggest impurity site nuclear magnetic resonance as a suitable experiment to probe the local boundstates that is peculiar to the +-s-wave state. We find that the +-s-wave model is mapped to a chiral dx2-y2+-idxy-wave, reflecting the unconventional nature of the sign reversing order parameter. For a quantum magnetic impurity, interband scattering destabilizes the Kondo singlet.

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