Anisotropic conductivity tensor on a half-filled high Landau level

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We study two-dimensional interacting electrons in a weak perpendicular magnetic field with the filling factor ν≫ 1 and in the presence of a quenched disorder. As it is known, the unidirectional charge density wave state can exist near a half-filled high Landau level at low temperatures if disorder is weak enough. We show that the existence of the unidirectional charge density wave state at temperature T<Tc where Tc is the transition temperature leads to the anisotropic conductivity tensor. We find that the anisotropic part of conductivity tensor is proportional to (Tc-T)/Tc below the transition in accordance with the experimental findings. The order parameter fluctuations wash out the mean-field cusp at T=Tc and the conductivity tensor becomes anisotropic even above the mean-field transition temperature Tc.