p -wave pairing in a two-component Fermi system with unequal population: Weak-coupling BCS to strong-coupling BEC regimes
Renyuan Liao, Florentin Popescu, Khandker Quader
We study $p$-wave pairing in a two-component Fermi system with unequal population across weak-coupling BCS to strong-coupling BEC regimes. We find a rich ${m}_{s}=0$ spin triplet $p$-wave superfluid (SF) ground state (GS) structure as a function of population imbalance. Under a phase stability condition, the ``global'' energy minimum is given by a multitude of ``mixed'' SF states formed of linear combinations of $m=\ifmmode\pm\else\textpm\fi{}1,0$ substates of the $\ensuremath{\ell}=1$ orbital angular momentum state. Except for the ``pure'' SF states ($\ensuremath{\ell}=1,m=\ifmmode\pm\else\textpm\fi{}1$), other states exhibit oscillation in energy with the relative phase between the constituent gap amplitudes. We also find states with ``local'' energy minimum that can be stable at higher polarizations, suggesting a quantum phase transition between the ``global'' and ``local'' minima phases driven by polarization. We relate the local and global minimum states to Morse and non-Morse critical points. We calculate the variations of the ground state energy with a relative phase angle, coupling, and polarization, and discuss possible consequences for experiments.
arXiv:0711.4594•Physical Review B•Oct 10, 2013•6 citations