Superadiabatic Approach to Quantum Geometric Transport

We introduce a nonadiabatic approach to study nonlinear transport phenomena by combining quantum evolutions of superadiabatic states and semiclassical transport theories. Different from conventional adiabatic-switching methods, our approach is capable of avoiding numerical divergence and unveiling underlying quantum geometric contributions simultaneously. Based on the superadiabatic approach, we find that the intrinsic nonlinear conductance is determined by the Berry connection polarizability on the Fermi surface. Incorporation of numerical results shows that our approach reproduces qualitative nonlinear transport in \mathcalP \mathcalT-symmetric antiferromagnets.