Unpaired and spin-singlet paired states of a two-dimensional electron gas in a perpendicular magnetic field

Abstract

We present a variational study of both unpaired and spin-singlet paired states induced in a two-dimensional electron gas at low density by a perpendicular magnetic field. It is based on an improved circular-cell approximation which leads to a number of closed analytical results. The ground-state energy of the Wigner crystal containing a single electron per cell in the lowest Landau level is obtained as a function of the filling factor $ν$: the results are in good agreement with those of earlier approaches and predict $ν_{c} \approx 0.25$ for the upper filling factor at which the solid-liquid transition occurs. A novel localized state of spin-singlet electron pairs is examined and found to be a competitor of the unpaired state for filling factor $ν>1$. The corresponding phase boundary is quantitatively displayed in the magnetic field-electron density plane.

19 pages, 8 figures, submitted to Phys. Rev. B on 7th April 2001. to appear in Phys. Rev. B