3 0 Se p 20 02 Spin - polarized stable phases of the 2 - D electron fluid at finite temperatures .

The Helmholtz free energy F of the interacting 2-D electron fluid is calculated nonperturbatively using a mapping of the quantum fluid to a classical Coulomb fluid [Phys. Rev. Letters, 87, 206 (2002)]. For density parameters rs such that ∼ 25 < rs, the fluid is unpolarized at all temperatures t = T/EF , where EF is the Fermi energy. For lower densities, the system becomes fully spin polarized for t smaller than ∼ 0.35, and partially polarized for ∼ 0.35 < t < 2, depending on the density. At rs ∼ 25 − 30, and t ∼ 0.35, an ”ambispin” phase where F is almost independent of the spin polarization is found. These results support recent claims, based on quantum Monte Carlo results, for a stable, fully spin-polarized phase at T = 0 for rs larger than ∼ 25− 26.