Magnetoresistance in the strongly insulating regime of GaAs two-dimensional hole systems

Magnetoresistance (MR) of GaAs two-dimensional hole systems (2DHSs) is investigated in the strongly insulating regime. By rotating the samples, the total magnetic field Btot and the perpendicular component B⊥ to the 2DHS are controlled independently. In the low-B⊥ region, a large positive B⊥-dependence of the longitudinal resistivity ρxx is observed when Btot is small, while it is replaced by a negative one when Btot is large. For higher B⊥, dips are observed in the ρxx vs B⊥ curve and the values of B⊥ at the dip depend on Btot. The results are discussed both in the framework of single-particle localization and in the framework of Wigner crystallization.