Competition of magnetic and pairing correlations in confined systems
speaker: Mario Cuoco (Laboratorio Regionale SuperMat, CNR-INFM e Dipartimento di Fisica 'E.R. Caianiello' -Università di Salerno)abstract: We investigate the competition between magnetic depairing interactions, due to spin-exchange mechanism andor to spin-dependent asymmetric bandwidths, and pairing coupling in confined systems. We present a detailed analysis of the quantum ground state in different regimes arising from the interplay between ferromagnetic and pairing correlations for different fillings. We find out that the occurrence of a ground state with coexisting spin-polarization and pairing correlations is enhanced when the asymmetric spin-dependent distribution of the single-particle energies is considered. We also consider the response to the imbalance of the chemical potential for the two spin states in the presence of pairing and magnetic interactions, comparing the ferromagnetic and the antiferromagnetic case. We show that the system is characterized by different regimes of quantum-pairing correlations that are strongly modified in the presence of a spin-polarized background. By examining the ground-state diagram in the entire space of interaction parameters we are able to identify several unconventional features. In the ferromagnetic case the pairing correlation is renormalized down as soon as the polarization starts to occur, thus the magnetization jumps at the interface between the paired ground state and the spin-polarized state. In the antiferromagnetic case, there exists a regime where strong pairing coexists with the polarization, so the magnetization exhibits a two-stage behavior. An abrupt change in the initial broken-pair number, when polarization sets in, is revealed when the pairing strength increases. We clarify the mechanisms underlying these unusual features in regime of unbalanced energies for the two spin states and obtain various analytic results for the detailed ground-state transitions.
timetable:
Thu 19 Jul, 17:00 - 17:25, Aula Dini
documents:
Cuoco.pdf
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