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Journal of the Physical Society of Japan

Spin Imbalance Effect on Josephson Junction and Grey Soliton

Ryosuke Yoshii, Giacomo Marmorini, Muneto Nitta

Published Aug 24, 2012• 4 citations
Publisher

Abstract

We study spin imbalance effects on the Josephson junction of superconductors under a strong magnetic field and the grey soliton in spin-polarized ultracold Fermi gas. We obtain the exact solution for the condensates with arbitrary spin imbalance and the fermion spectrum perturbatively in the presence of small spin imbalance.
DOI
10.1143/jpsj.81.094704

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A minimal coupling quantum hydrodynamic model of spin-1/2 fermions at the full spin polarization corresponding to a nonlinear Schrodinger equation is considered. The nonlinearity is primarily caused by the Fermi pressure. It provides an effective repulsion between fermions. However, there is the additional contribution of the short-range interaction appearing in the third order by the interaction radius. It leads to the modification of the pressure contribution. Solitons are considered for the infinite medium with no restriction on the amplitude of the wave. The Fermi pressure leads to the soliton in form of the area of decreased concentration. However, the center of solution corresponding to the area of minimal concentration has nonzero value of concentration. Therefore, the grey soliton is found. Soliton exist if the speed of its propagation is below the Fermi velocity. Keywords: degenerate fermions, hydrodynamics, non-linear Schrodinger equation, dark soliton, Fermi pressure.