Enhanced vortex pinning with possible antiferromagnetic order in FeSe under pressure

The strong coupling between magnetic, structural, and electronic degrees of freedom is a prominent feature of Fe-based superconductors. However, the relationship between the degrees of freedom and vortex dynamics remains unclear. In this paper, we measure the vortex pinning energy ${U}₀/{k}_{\mathrm{B}}$ within the thermally activated flux-flow regime with respect to the pressure-induced phases in a FeSe single crystal. We show that the dependence of ${U}₀/{k}_{\mathrm{B}}$ on pressure, measured at a magnetic field higher than the crossover field ${H}_{\mathrm{cr}}$, follows a trend like those of critical temperature ${T}_c(p)$ and the average Fermi velocity ${\overline{v}}_{\mathrm{F}}(p)$. On the other hand, at magnetic fields lower than ${H}_{\mathrm{cr}}, {U}₀/{k}_{\mathrm{B}}$ increases remarkably before reaching the pressure at which antiferromagnetic (AFM) long-range order occurs. Our results suggest the presence of additional pinning sites, possibly AFM domain boundaries, correlated with the enhanced ${U}₀/{k}_{\mathrm{B}}$. In addition, in this paper, we provide a universal description of the vortex dynamics in FeSe.