Anisotropic transport for the ν = 2/5fractional quantum Hall state at intermediate magnetic fields

Abstract

The ν = 2/5state is spin unpolarized at weak magnetic field and fully polarized at strong field.At intermediate field, a plateau of half the maximal polarization is observed. Westudy this phenomenon in the framework of composite fermion (CF) theory. Dueto the mixing of the CF Landau levels (LLs), the unidirectional charge/spindensity wave state of CFs is lower in energy than the Wigner crystal. This meansthat transport anisotropy, similar to that for electrons in higher Landau levels athalf-filling, may appear in this fractional quantum Hall state when theexternal magnetic field is in an appropriate range. When the magnetic fieldis tilted, the easy transport direction is perpendicular to the directionof the in-plane field. Varying the partial filling factor of CF LLs from0 to1, wefind that the energy minimum occurs in the vicinity of a half.