Anomalous heat current driven by a Berry curvature dipole in (Pb_1-xSn_x)_1-yIn_yTe

Materials displaying a Berry curvature dipole in their electronic structure can enable nonlinear transport effects. The recently discovered nonlinear Hall effect exists without the presence of magnetic field or magnetization¹. This effect belongs to a larger family of new transport phenomena predicted theoretically to exist.² Here we present experimental evidence for a new type of thermoelectric transport anomaly that arises in the absence of magnetization due to the Berry curvature dipole.  It is realized in the ferroelectric phase of (Pb_1-xSn_x)_1-yIn_yTe single crystals. The nonlinear Hall effect is experimental evidence that these crystals host giant Berry curvature dipoles¹. Here, we show the Berry curvature dipole also causes anomalous changes in thermal conductivity as a function of an external electric field E, with the magnitude of the change proportional to E. In (Pb_0.59Sn_0.41)_0.97In_0.03Te, the Berry curvature dipole is predicted to peak with  magnitude carrier density, corresponding to measurements above 100 K. In 2 samples, we observed a linear relationship between imposed electric field  along the polar axis and the antisymmetric components of thermal conductivity  in the plane normal to z. The antisymmetrized thermal conductivity can be as high as  6.0 x 10^-3  W m⁻¹ K⁻¹ at 305 K and 200 V m^-1. The observed dependence of thermal conductivity on E-field are in agreement with theoretical predictions.<sup>2

1</sup> C.-L. Zhang, T. Liang, Y. Kaneko, N. Nagaosa, and Y. Tokura, “Giant Berry curvature dipole density in a ferroelectric Weyl semimetal,” Npj Quantum Mater. 7(1), 103 (2022).

² Xu Yang, Brian Skinner, “Nonlinear thermoelectric effects as a means to probe quantum geometry”, arXiv:2505.00086 (2025)