Enhanced superconductivity by correlations between two Kondo impurities

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• 作者：R. Allub ; ¹ ; ^a ; ^{allub@cab.cnea.gov.ar}
• 关键词：Local moment in compounds and alloys ; Kondo effect ; Valence fluctuations ; Heavy fermions ; Magnetic impurity interactions
• 刊名：Physica B
• 出版年：2011
• 出版时间：15 April 2011
• 年：2011
• 卷：406
• 期：9
• 页码：1738-1743
• 全文大小：243 K

文摘

We study the interplay between magnetic correlations of two Kondo impurities and superconducting singlet pairing. Performing a Schrieffer–Wolff transformation in the zero-bandwidth limit of the two-impurity Anderson model we obtain the Hamiltonian of two magnetic impurities and we add a superconducting term to the conduction electrons. The model allows us to study the effect of the magnetic correlation between the impurities on the superconducting ground state. At zero temperature, different superconducting ground states can be obtained depending on the magnitude of magnetic coupling between S₁ and S₂. For increasing coupling, the superconducting region is enlarged showing an interesting result: in the strong coupling limit, where the impurities are in a very strong ferromagnetic correlation state, half of the conduction electrons are decoupled from the local moments of the impurities and take advantage of the superconducting pairing lowering the ground state energy. On the contrary, when the coupling between S₁and S₂ decreases, the scenario of the two independent Kondo impurities in presence of superconductivity emerges and all the conduction electrons are involved in the pair breaking physics. At finite temperature, we obtain the phase diagram and we observe a region of parameters where the re-entrance phenomenon occurs.