Orientational pinning of the striped phase in a quantum hall liquid

A new class of collective states, which are assumed to be due to the spontaneous formation of a charge density wave (striped phase) upon filling high Landau levels, was recently observed in a 2D electron system based on GaAs/AlGaAs(001). The following unsolved problem is considered in the work: what is the reason for stripe pinning along the crystallographic direction [110]? It is shown that the effective mass of 2D electrons is anisotropic for a single heterojunction (001) A(3)B(5). This natural anisotropy is due to the C-2v symmetry of the heterointerface and, even being weak (0.1%), can govern the stripe direction. A magnetic field parallel to the interface induces magnetic anisotropy of effective mass. The competition of these two types of anisotropy (natural and magnetic) provides a quantitative description of the experiment. (C) 2000 MAIK Nauka/Interperiodica.