Double sign reversal of the mixed-state Hall effect in exfoliated FeSe flakes
Phys. Rev. B 113, 125411 – Published 9 March, 2026
DOI: https://doi.org/10.1103/5mqr-wqt8
Abstract
The Hall effect in the superconducting mixed state serves as a crucial probe of vortex dynamics. Here, we report a systematic magnetotransport study on the vortex Hall effect in exfoliated FeSe flakes with varying thickness. In flakes of intermediate thickness (e.g., 159 nm), the Hall resistivity in the superconducting mixed state exhibits a double sign reversal as a function of temperature, characterized by a pronounced peak-dip structure. This behavior evolves with magnetic field and current, and is qualitatively consistent with the predictions of vortex dynamics theory (Wang, Dong, and Ting theory). However, the complex evolution of the sign reversal across different thicknesses cannot be explained by existing models. We propose a unified physical picture that incorporates Magnus force, equivalent Lorentz force, and carrier-type effects to explain the sign reversals and their thickness-dependent evolution. Finally, we discuss the connection between the unconventional Hall response and the microscopic origin of vortex pinning in FeSe. Our results advance the understanding of vortex transport and the anomalous Hall effect in iron-based superconductors.
