Phase transition of ferromagnetic Fermi liquids

Takeo Izuyama

P. G. J. van Dongen, Götz Silvester Uhrig, E. Mueller-Hartmann

Börje Johansson

Joshuah T. Heath, Kevin S. Bedell

For nearly a century, the Stoner model has dominated research in itinerant ferromagnetism, yet recent work on ultracold, optically trapped Fermi gases suggests that phase separation of spins occurs independent of long-range magnetic order. In this paper, we consider the breakdown of the Stoner criterion in a Landau-Fermi liquid with weak non-zero gauge field. Due to a process analogous to Kohn's theory of a metal-insulator transition, we find the stability of a Fermi liquid phase in the absence of non-quasiparticle contributions to the response is strongly dependent on Landau parameters of mixed partial waves. Our work paves the way for the description of novel spintronic hardware in the language of Landau-Fermi liquid transport.

Paweł Jakubczyk

Jordi Pera, J. Casulleras, Jordi Boronat

Itinerant ferromagnetism is one of the most-studied quantum phase transitions, the transition point and the nature of this phase transition being widely discussed. In dilute Fermi liquids, this analysis has been carried out up to second order in the gas parameter, where the results for any spin degeneracy are universal in terms of only the s -wave scattering length a 0 . We extend this analysis to third order, where energies depend not only on a 0 , but also on the s -wave effective range r 0 and the p -wave scattering length a 1 . The introduction in the theory of these new parameters changes the transition point, with respect to the second-order estimation, and also can modify the nature of the phase transition itself. We analyze these interaction effects on the phase transition for different spin values. The emerging phase diagram shows that the type of ferromagnetic transition changes dramatically as a function of r 0 and a 1 and, importantly, that this classification is not solely determined by the spin value, as happens at second order.