Spin-polarized stable phases of the 2-D electron fluid at finite temperatures

TL;DR

This study nonperturbatively calculates the Helmholtz free energy of a 2-D electron fluid, revealing temperature-dependent spin polarization phases and supporting the existence of a stable, fully spin-polarized phase at finite temperatures for high density parameters.

Contribution

It introduces a nonperturbative method to analyze spin polarization phases of the 2-D electron fluid at finite temperatures, extending prior zero-temperature quantum Monte Carlo findings.

Findings

Unpolarized phase at rs<~25 for all temperatures.

Full spin polarization occurs below t~0.35 at lower densities.

An 'ambispin' phase with near-independent free energy is observed near rs~25-30.

Abstract

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, vol. 87, 206404 (2001)]. For density parameters rs such that rs<~25, 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<~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 fluid phase at T = 0 for rs larger than about 25-26.