  Electrically defined semiconductor quantum dots are attractive systems for
spin manipulation and quantum information processing. Heavy-holes in both Si
and GaAs are promising candidates for all-electrical spin manipulation, owing
to the weak hyperfine interaction and strong spin-orbit interaction. However,
it has only recently become possible to make stable quantum dots in these
systems, mainly due to difficulties in device fabrication and stability. Here
we present electrical transport measurements on holes in a gate-defined double
quantum dot in a $\mathrm{GaAs/Al_xGa_{1-x}As}$ heterostructure. We observe
clear Pauli spin blockade and demonstrate that the lifting of this spin
blockade by an external magnetic field is highly anisotropic. Numerical
calculations of heavy-hole transport through a double quantum dot in the
presence of strong spin-orbit coupling show quantitative agreement with
experimental results and suggest that the observed anisotropy can be explained
by both the anisotropic effective hole g-factor and the surface Dresselhaus
spin-orbit interaction.
