Theoretical evidence of the Berry-phase mechanism in anomalous Hall transport: First-principles studies of CuCr2Se4-xBrx

To justify the origin of the anomalous Hall effect (AHE), it is highly desirable to have the system parameters tuned continuously. By quantitative calculations, we show that the doping-dependent sign reversal in CuCr2Se4-xBrx, observed but not understood, is nothing but direct evidence for the Berry-phase mechanism of the AHE. Systematic calculations explain well the experiment data for the whole doping range where the impurity scattering rate is changed by several orders with Br substitution. Further sign change is also predicted, which may be tested by future experiments.