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 U0/kB 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 U0/kB on pressure, measured at a magnetic field higher than the crossover field Hcr, follows a trend like those of critical temperature Tc(p) and the average Fermi velocity v¯F(p). On the other hand, at magnetic fields lower than Hcr, U0/kB 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 U0/kB. In addition, in this paper, we provide a universal description of the vortex dynamics in FeSe.
Bibliographical noteFunding Information:
Y.J. was supported by the National Research Foundation of Korea (NRF; Grants No. 2018K2A9A1A06069211 and No. 2019R1A2C1089017). W.K. acknowledges support by the NRF (Grants No. 2018R1D1A1B07050087 and No. 2018R1A6A1A03025340). J.S.K. was supported by the IBS through the Center for Artificial Low Dimensional Electronic Systems (No. IBS-R014-D1) and by the NRF through SRC (Grant No. 2018R1A5A6075964) and the Max Planck-POSTECH Center for Complex Phase Materials (Grant No. 2016K1A4A4A01922028). A portion of this work was performed at the National High Magnetic Field Laboratory, which is supported by the National Science Foundation Cooperative Agreement No. DMR-1644779* and the State of Florida.
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