Interface-induced Berry-curvature dipole and second-order nonlinear Hall effect in two-dimensional Fe5GeTe2

The second-order nonlinear Hall effect (NLHE), driven by the Berry-curvature dipole (BCD), quantum metrics, and disorder-related mechanisms, have potential in energy harvesting and signal doubling. However, for a large class of known materials, in which inversion symmetry is preserved, the BCD and NLHE are strictly zero. Here, we report that, by interface modulation through ${\mathrm{Al}}_{x}{\mathrm{O}}_{3}$-assisted exfoliation, a strong NLHE is generated in few-layer ${\mathrm{Fe}}_{5}{\mathrm{Ge}\mathrm{Te}}_{2}$, in which both the BCD and disorder-related contributions are in principle prohibited due to its $R\overline{3}m$ lattice symmetry. Scaling analysis indicates the existence of a large BCD reaching $\mathrm{\ensuremath{\Lambda}}\ensuremath{\approx}150\phantom{\rule{0.25em}{0ex}}\text{nm}$. The negative results from ${\mathrm{Fe}}_{5}{\mathrm{Ge}\mathrm{Te}}_{2}$ devices on ${\mathrm{Si}\mathrm{O}}_{2}$ substrates confirm that the interface between ${\mathrm{Fe}}_{5}{\mathrm{Ge}\mathrm{Te}}_{2}$ and ${\mathrm{Al}}_{x}{\mathrm{O}}_{3}$ is responsible for the observed NLHE, revealing an interface-induced BCD, which has never been reported before. Our study provides a feasible way to generate NLHE in materials with inversion symmetry, expanding the material family for NLHE research and inspiring potential applications due to the advantages in mass production.