Unconventional superconducting phases in a correlated two-dimensional Fermi gas of nonstandard quasiparticles: a simple model

• Published in: Journal of physics. Condensed matter Vol. 22; no. 35; p. 355702
• Main Authors: Kaczmarczyk, Jan, Spałek, Jozef
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 08.09.2010; Institute of Physics
• Subjects: Boundaries; Condensed matter; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Correlation; Exact sciences and technology; Nonconventional mechanisms (spin fluctuations, polaron and bipolaron theory, rvb theory, anyon mechanism, marginal fermi liquid, luttinger liquid, etc.); Phase diagrams; Phases; Physics; Robustness; Superconductivity; Theory and models of superconducting state; Two dimensional; Effective field approximation; Metamagnetism; Quasiparticles; Electron correlations; Phase diagrams; Fermi gas; Superconductivity model; Magnetic field effects; Pairing; BCS theory
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/22/35/355702

We discuss a detailed phase diagram and other microscopic characteristics on the applied magnetic field-temperature (H(a)-T) plane for a simple model of a correlated fluid represented by a two-dimensional (2D) gas of heavy quasiparticles with masses dependent on the spin direction and the effective field generated by the electron correlations. The consecutive transitions between the Bardeen-Cooper-Schrieffer (BCS) and the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phases are either continuous or discontinuous, depending on the values of H(a) and T. In the latter case, weak metamagnetic transitions occur at the BCS-FFLO boundary. We single out two different FFLO phases, as well as a re-entrant behaviour of one of them at high fields. The results are compared with those for ordinary Landau quasiparticles in order to demonstrate the robustness of the FFLO states against the BCS state for the case with spin-dependent masses (SDM). We believe that the mechanism of FFLO stabilization by SDM is generic: other high-field low-temperature (HFLT) superconducting phases should benefit from SDM as well.