Fermi surface of composite fermions and one-particle excitations atν=12:Effect of band-mass anisotropy

Abstract

We study the ground state and one-particle excitations in the half-filled Landau level when a two-dimensional electron gas is characterized by an anisotropic band-mass tensor. Using asymptotic Ward identities of the Chern-Simons theory for $\ensuremath{\nu}=\frac{1}{2},$ we show that a composite fermion Fermi surface is not renormalized by infrared gauge fluctuations so that its form is identical to that of an anisotropic electron Fermi surface in the absence of the magnetic field. It appears, however, that, despite the anisotropy of the Fermi surface, the composite fermion effective mass is almost isotropic. Possible experimental consequences of these effects are considered.