Effects of a parallel magnetic field on the ground-state magnetic properties of a two-dimensional electron gas

We study the magnetic behavior and in particular the spin magnetization of an interacting two-dimensional electron gas in an in-plane magnetic field. The ground-state energy of the system is constructed using the correlation energy based on the recent quantum Monte Carlo (QMC) simulations as a function of density, spin polarization, and applied magnetic field. The critical magnetic field to fully spin polarize the system is obtained as a function of the electron density. The spin polarization as a function of the applied field (less than the critical field) for various densities is calculated. When the QMC parametrization is employed, we find that the two-dimensional electron system undergoes a first-order phase transition to a ferromagnetic state in the regions 0< rs <7 and 20< rs <25, where rs is the usual density parameter. For 7< rs <20 our calculations indicate a second-order transition unlike approximate theories.