FFLO states and quantum oscillations in mesoscopic superconductors and superfluid ultracold Fermi gases

摘要

We have studied the distinctive features of theFulde-Ferrel-Larkin-Ovchinnikov (FFLO) instability and phase transitions intwo--dimensional (2D) mesoscopic superconductors placed in magnetic field ofarbitrary orientation and rotating superfluid Fermi gases with imbalanced statepopulations. Using a generalized version of the phenomenologicalGinzburg-Landau theory we have shown that the FFLO states are strongly modifiedby the effect of the trapping potential confining the condensate. Thephenomenon of the inhomogeneous state formation is determined by the interplayof three length scales: (i) length scale of the FFLO instability; (ii) 2Dsystem size; (iii) length scale associated with the orbital effect causedeither by the Fermi condensate rotation or magnetic field component appliedperpendicular to the superconducting disc. We have studied this interplay andresulting quantum oscillation effects in both superconducting and superfluidfinite -- size systems with FFLO instability and described the hallmarks of theFFLO phenomenon in a restricted geometry. The finite size of the system isshown to affect strongly the conditions of the observability of switchingbetween the states with different vorticities.