A mean-field approach to Kondo-attractive-Hubbard model.

Autor: Costa NC; Instituto de Física, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil., de Lima JP, Paiva T, El Massalami M, Dos Santos RR
Jazyk: angličtina
Zdroj: Journal of physics. Condensed matter : an Institute of Physics journal [J Phys Condens Matter] 2018 Jan 31; Vol. 30 (4), pp. 045602.
DOI: 10.1088/1361-648X/aaa1ab
Abstrakt: With the purpose of investigating coexistence between magnetic order and superconductivity, we consider a model in which conduction electrons interact with each other, via an attractive Hubbard on-site coupling U, and with local moments on every site, via a Kondo-like coupling, J. The model is solved on a simple cubic lattice through a Hartree-Fock approximation, within a 'semi-classical' framework which allows spiral magnetic modes to be stabilized. For a fixed electronic density, n c , the small J region of the ground state (T  =  0) phase diagram displays spiral antiferromagnetic (SAFM) states for small U. Upon increasing U, a state with coexistence between superconductivity (SC) and SAFM sets in; further increase in U turns the spiral mode into a Néel antiferromagnet. The large J region is a (singlet) Kondo phase. At finite temperatures, and in the region of coexistence, thermal fluctuations suppress the different ordered phases in succession: the SAFM phase at lower temperatures and SC at higher temperatures; also, reentrant behaviour is found to be induced by temperature. Our results provide a qualitative description of the competition between local moment magnetism and superconductivity in the borocarbides family.
Databáze: MEDLINE