Sarma phase in relativistic and non-relativistic systems

Abstract

We investigate the stability of the Sarma phase in two-component fermion systems in three spatial dimensions. For this purpose we compare strongly-correlated systems with either relativistic or non-relativistic dispersion relation: relativistic quarks and mesons at finite isospin density and spin-imbalanced ultracold Fermi gases. Using a Functional Renormalization Group approach, we resolve fluctuation effects onto the corresponding phase diagrams beyond the mean-field approximation. We find that fluctuations induce a second order phase transition at zero temperature, and thus a Sarma phase, in the relativistic setup for large isospin chemical potential. This motivates the investigation of the cold atoms setup with comparable mean-field phase structure, where the Sarma phase could then be realized in experiment. However, for the non-relativistic system we find the stability region of the Sarma phase to be smaller than the one predicted from mean-field theory. It is limited to the BEC side of the phase diagram, and the unitary Fermi gas does not support a Sarma phase at zero temperature. Finally, we propose an ultracold quantum gas with four fermion species that has a good chance to realize a zero-temperature Sarma phase.

version published in Phys.Lett.B; 10 pages, 5 figures

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Cited by in corpus (5)

• Ising and Gross-Neveu model in next-to-leading order
• Phase structure of mass- and spin-imbalanced unitary Fermi gases
• Continuum Goldstone spectrum of two-color QCD at finite density with staggered quarks
• Renormalization theory for the Fulde-Ferrell-Larkin-Ovchinnikov states at $T>0$
• 3-dimensional QCD phase diagram with pion condensate in the NJL model