Quantized nonlinear Hall effect from chiral monopole

The nonlinear Hall effect arises in materials without inversion symmetry, and the intrinsic contribution is typically from the Berry curvature dipole of nonuniversal Fermi pockets. Here we propose that the nonlinear Hall effect can reach quantization in chiral Weyl semimetals without mirror symmetries. The energy shift between a pair of Weyl nodes leads to chirally asymmetric intranode relaxation, and the net trace of nonlinear Hall conductivity is thus quantized in units of e3/ℏ2 and determined by the sum of monopole charge weighted by the transport relaxation time. Our theory also applies to mirror symmetric Weyl and Dirac semimetals with chiral anomalies. Additionally, besides dc transport probes, we anticipate that nonlinear circular dichroism measurements can detect chiral asymmetry-induced currents.