Disclination unbinding transition in quantum Hall liquid crystals - art. no. 115312

We derive the long-wavelength elastic theory for the quantum Hall smectic s tate starting from the Hartree-Fock approximation. Dislocations in this sta te lead to an effective nematic model for T>0, which undergoes a disclinati on unbinding transition from a phase with algebraic orientational order int o an isotropic phase. We obtain transition temperatures that are in qualita tive agreement with recent experiments that have observed large anisotropie s of the longitudinal resistivities in half-filled Landau levels, lending c redence to the liquid crystal interpretation of experiments.