CDW Ground States and Electron-Hole Symmetry of a Two-Dimensional Electron System in Strong Magnetic Fields

Abstract

The ground state of a two-dimensional electron system in a strong magnetic field is studied in the Hartree-Fock approximation for the case of a half-filled ground Landau level. Due consideration is given to consequences of the electron-hole symmetry, which is found to lead to a nonmetallic CDW ground state. The Hartree-Fock integral equations are solved numerically with full account of higher harmonics. The result shows that the ground state is not a triangular CDW, in spite of the most favorable Madelung energy, but a square CDW with the electron-hole symmetry spontaneously broken. Detailed results for band structures, density patterns and cohesive energies are presented.