We present a comprehensive study of the vortex pinning and dynamics in a high-quality FeSe single crystal, which is free from doping introduced inhomogeneities and charged quasi-particle-scattering because of its innate superconductivity. Critical current density, Jc, is found to be almost isotropic, and reaches a value ∼ 3 × 104 A/cm2 at 2 K (self-field) for both H∥c and ab. The normalized magnetic relaxation rate S (= ∣dlnM/dlnt∣) shows a temperature insensitive plateau behavior in the intermediate temperature range with a relatively high creep rate (S∼ 0.02 under zero field), which is interpreted in the framework of the collective creep theory. A crossover from the elastic to plastic creep is observed, while the fish-tail effect is absent for both H∥c and ab. Based on this observation, the origin of the fish-tail effect is also discussed. Combining the results of Jc and S, vortex motion in FeSe single crystal is found to be dominated by sparse strong point-like pinning from nm-sized defects or imperfections. The weak collective pinning is also observed and proved in the form of large bundles. Besides, the vortex phase diagram of FeSe is also constructed and discussed.
@article{arxiv.1510.05753,
title = {Critical current density, vortex dynamics, and phase diagram of FeSe single crystal},
author = {Yue Sun and Sunseng Pyon and Tsuyoshi Tamegai and Ryo Kobayashi and Tatsuya Watashige and Shigeru Kasahara and Yuji Matsuda and Takasada Shibauchi},
journal= {arXiv preprint arXiv:1510.05753},
year = {2015}
}