Stability of superfluid phases in the 2D spin-polarized attractive Hubbard model

作者：Kujawa Cichy A^*; Micnas R

来源：EPL, 2011, 95(3): 37003.

DOI：10.1209/0295-5075/95/37003

We study the evolution from the weak coupling (BCS-like limit) to the strong coupling limit of tightly bound local pairs (LPs) 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(up arrow) = t(down arrow)), 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 SCM 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-vertical bar U vertical bar and t(up arrow)/t(down arrow)-vertical bar U vertical bar ground-state phase diagrams. We also construct the finite temperature phase diagrams for both t(up arrow) = t(down arrow) and t(up arrow) not equal t(down arrow) and analyze the possibility of occurrence of a spin-polarized KT superfluid.

• 出版日期2011-8