Stability of superfluid phases in the 2D Spin-Polarized Attractive Hubbard Model

Abstract

We study the evolution from the weak coupling (BCS-like limit) to the strong coupling limit of tightly bound local pairs (LP's) with increasing attraction, in the presence of the Zeeman magnetic field ($h$) for $d=2$, within the spin-polarized attractive Hubbard model. The broken symmetry Hartree approximation {as well as the} strong coupling expansion are used. We also apply the Kosterlitz-Thouless (KT) scenario to determine the phase coherence temperatures. For spin independent hopping integrals ($t^{\uparrow }=t^{\downarrow }$), we find no stable homogeneous polarized superfluid (SC${}_M$) state in the ground state for the strong attraction and obtain that for a two-component Fermi system on a 2D lattice with population imbalance, phase separation (PS) is favoured for a fixed particle concentration, even on the LP (BEC) side. We also examine the influence of spin dependent hopping integrals (mass imbalance) on the stability of the SC${}_M$ phase. We find a topological quantum phase transition (Lifshitz type) from the unpolarized superfluid phase (SC${}_0$) to SC${}_M$ and tricritical points in the ($h-|U|$) and ($t^{\uparrow }/t^{\downarrow }-|U|$) ground state phase diagrams. We also construct the finite temperature phase diagrams for both $t^{\uparrow }=t^{\downarrow }$ and $t^{\uparrow }\ne t^{\downarrow }$ and analyze the possibility of occurrence of a spin polarized KT superfluid.

7 pages, 4 figures

References in corpus (9)

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• Two-species fermion mixtures with population imbalance
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Cited by in corpus (8)

• Fulde-Ferrell states and Berezinskii-Kosterlitz-Thouless phase transition in two-dimensional imbalanced Fermi gases
• The magnetic field induced phase separation in a model of a superconductor with local electron pairing
• Fluctuations of imbalanced fermionic superfluids in two dimensions induce continuous quantum phase transitions and non-Fermi liquid behavior
• Reentrant Fulde-Ferrell-Larkin-Ovchinnikov superfluidity in the honeycomb lattice
• Effective potential and quantum criticality for imbalanced Fermi mixtures
• Feasibility of a Fulde-Ferrell-Larkin-Ovchinnikov superfluid Fermi atomic gas
• Spin-polarized superconducting phase in semiconducting system with next-nearest-neighbor hopping on the honeycomb lattice
• Connection between the semiconductor--superconductor transition and the spin-polarized superconducting phase in the honeycomb lattice