Bilayer materials with layer‑locked Berry curvature dipoles can toggle their nonlinear Hall response under an applied gate field, offering a pathway to new nonlinear quantum devices Stained glass window and smartphone (Courtesy: Shutterstock/Jorge Isaac) The Hall effect is a voltage that appears across a material when a current flows through it in the presence of an external magnetic field. The nonlinear Hall effect, however, can occur without a magnetic field if the material’s internal structure is asymmetric. It typically appears under an AC or oscillating electric field, and the resulting Hall voltage scales with the square of the input current, making it a nonlinear response. Researchers are interested in this effect because it could enable new types of sensors, low‑power logic elements, and electrically switchable quantum devices. But so far, the nonlinear Hall effect has been difficult to control in a reliable, switchable way.…