Fig. S2.

Illustration of the larger range of values for the parameter ε over which the approximation Eq. S28 is accurate. Parameters are given in Table S2, with the exception of $p_x$ and ε, which are varied. Note that this figure is similar to Fig. 2, in the main text, but plotted over a greater range of ε and ${\varphi }_x-{\varphi }_y.$ The parameter region plotted in black is that for which $\kappa \delta >r{p}_x.$