Nonlinear Hall Effect in Dirac/Weyl Semimetals and Terahertz Detection

We propose a method for broadband long-wavelength photodetection using the nonlinear Hall effect in Dirac/Weyl semimetals with/without magnetic field. With intrinsicly tiled spectrum or induced chirality imbalance, the net Berry curvature gives rise to a nonlinear current, with inherently quadratic relation between transverse current and input voltage. This effect is then used to rectify the incident terahertz or infrared electric field into a direct current, without invoking any diode. Our photodetector operates at zero external bias with fast response speed and has zero threshold voltage. Remarkably, the intrinsic current responsivity due to the Berry curvature mechanism is a material property independent of the incident frequency or the scattering rate, which can be evaluated from first-principles electronic structure calculations. We identify the Weyl semimetal NbP and ferroelectric semiconductor GeTe for terahertz/infrared photodetection with large current responsivity without external bias.