Nonlinear Nernst effect in bilayer WTe2

Unlike the linear anomalous Nernst effect, the nonlinear anomalous Nernst effect (NLANE) can survive in an inversion symmetry broken system even in the presence of time-reversal symmetry. Using semiclassical Boltzmann transport theory, we study the nonlinear anomalous Nernst effect that arises as the second-order response function to the applied temperature gradient. We find that the nonlinear Nernst current, which flows perpendicular to the temperature gradient even in the absence of a magnetic field, arises due to the Berry curvature of the states near the Fermi surface, and thus is associated with purely a Fermi surface contribution. We apply these results to bilayer WTe₂, which is an inversion broken but time-reversal symmetric type-II Weyl semimetal supporting chiral Weyl fermions. By tuning the spin-orbit coupling, we show that the sign of the NLANE can change in this system. Together with the angular dependence, we calculate the temperature and chemical potential dependencies of NLANE in bilayer WTe₂, and predict specific experimental signatures that can be checked in experiments.