Fig. 4: Simulation results for a model with ultrathin anisotropic surfaces. | Nature Communications

Fig. 4: Simulation results for a model with ultrathin anisotropic surfaces.

From: Anisotropic resistance with a 90° twist in a ferromagnetic Weyl semimetal, Co2MnGa

Fig. 4

a, b Comparison of the experimental (red) and simulated (shades of blue) resistances in the δ = 10 nm thin-surface model. For a range of α = {10, 100, 500, 1000}, β was tuned so that the simulated R12,43 (low-conductance axis) matched the experimental resistance within 0.5%. The optimal β for these α were found to be 5.76, 4.31, 3.65, and 3.4 × 104, respectively. Panel a (b) presents the results with the current contacts \(\overrightarrow{ij}\)\(\parallel \hat{{{{{{{{\bf{x}}}}}}}}},\hat{{{{{{{{\bf{y}}}}}}}}}\) (\(\parallel \hat{{{{{{{{\bf{z}}}}}}}}}\)). Due to the C4I symmetry, it suffices to simulate only \(\frac{1}{4}\) of the possible four-point resistance configurations. c This plot shows that although the experimentally observed anomalous resistances can be recreated for a range of α, no anisotropy arises for β < 104. Without a large suppression of the out-of-plane conductivity in the surfaces, the anomalous resistances revert to the isotropic-equivalent values. d This diagram shows the surface potential contours that arise when current is directed \(\parallel \hat{{{{{{{{\bf{z}}}}}}}}}\), ij = 11'. The range has been limited to ± 1 Ω about the C4I-symmetric point at the midpoint of the \(3{3}^{{\prime} }\) edge in order to resolve the contours that extend across the sample. The spacing between contours is 0.01 Ω. They appear to have discrete jumps between the two faces because the thickness of the ultrathin anisotropic surfaces cannot be resolved (1% of the total slab thickness).

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