Evidence of spontaneous spin polarization in the two-dimensional electron gas

A. R. GOÑI; P. GIUDICI; F. A. REBOREDO; C. R. PROETTO; C. THOMSEN

PHYSICAL REVIEW B

AMER PHYSICAL SOC

Año: 2004 vol. 70 p. 195331 - 195334

1098-0121

Density-functional calculations using an exact exchange potential for a two-dimensional electron gas (2DEG) formed in a GaAs single quantum well predict the existence of a spin-polarized phase, when an excited subband becomes slightly populated. Direct experimental evidence is obtained from low-temperature and low-excitation power photoluminescence (PL) spectra, which display the sudden appearance of a sharp emission peak below the energy of the optical transition from the first excited electron subband upon its occupation. The behavior of this PL feature in magnetic fields applied in-plane as well as perpendicular to the 2DEG indicate the formation of spin-polarized domains in the excited subband with in-plane magnetization. The strong enhancement of exchange-vertex corrections observed in inelastic light scattering spectra by spin-density excitations of a slightly occupied first-excited subband also speaks for the appearance of magnetic ordering.