Carrier dynamics acquire a new character in the presence of Bloch-band Berrycurvature, which naturally arises in gapped Dirac materials (GDMs). Here weargue that photoresponse in GDMs with small band gaps is dramatically enhancedby Berry curvature. This manifests in a giant and saturable Hallphotoconductivity when illuminated by circularly polarized light. Unlike Hallmotion arising from a Lorentz force in a magnetic field, which impedeslongitudinal carrier motion, Hall photoconductivity arising from Berrycurvature can boost longitudinal carrier transport. In GDMs, this results in ahelicity-dependent photoresponse in the Hall regime, where photoconductivity isdominated by its Hall component. We find that the induced Hall conductivity perincident irradiance is enhanced by up to six orders of magnitude when movingfrom the visible regime (with corresponding band gaps) to the far infrared.These results suggest that narrow-gap GDMs are an ideal test-bed for the uniquephysics that arise in the presence of Berry curvature, and open a new avenuefor infrared and terahertz optoelectronics.
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