Numerical Studies of Quantum Hall Ferromagnetism in Two-Subband Systems

We carry out a numerical study of the quantum Hall ferromagnetism in a two-subband system using a set of experimental parameters in a recently experiment [X. C. Zhang, I. Martin, and H. W. Jiang, Phys. Rev. B \textbf{74}, 073301 (2006)]. Employing the self-consistence local density approximation for growth direction wave function and the Hartree-Fock theory for the pseudospin anisotropy energy, we are able to account for the easy-axis and easy-plane quantum Hall ferromagnetism observed at total filling factor $\nu = 3$ and $\nu= 4$, respectively. Our study provides some insight of how the anisotropy energy, which highly depends upon the distribution of growth direction wave functions, determines the symmetry of the quantum Hall ferromagnets.