Anisotropic transport in unidirectional lateral superlattice around half filling of the second Landau level

We have observed marked transport anisotropy in short period (a=92 nm) unidirectional lateral superlattices around filling factors ν=5/2 and 7/2: magnetoresistance shows a sharp peak for current along the modulation grating while a dip appears for current across the grating. By altering the ratio $a/l$ (with l=√/eB_⊥ the magnetic length) via changing the electron density nₑ, it is shown that the ν=5/2 anisotropic features appear in the range 6.6a/l7.2 varying their intensities, becoming most conspicuous at a/l6.7. The peak/dip broadens with temperature roughly preserving its height and depth up to 250 mK. Tilt experiments reveal that the structures are slightly enhanced by an in-plane magnetic field B_ perpendicular to the grating but are almost completely destroyed by B_ parallel to the grating. The observations suggest the stabilization of a unidirectional charge-density-wave or stripe phase by weak external periodic modulation at the second Landau level.