title: The upper critical field and its anisotropy in (Li1-xFex)OHFe1-ySe.
abstract: The temperature dependence of the upper critical field (Hc2) in a (Li1-xFex)OHFe1-ySe single crystal ([Formula: see text] K) has been determined by means of magnetotransport measurements down to 1.4 K both for inter-plane ([Formula: see text], [Formula: see text]) and in-plane ([Formula: see text], [Formula: see text]) field directions in static magnetic fields up to 14 T and pulsed magnetic fields up to 70 T. [Formula: see text] exhibits a quasilinear increase with decreasing temperature below the superconducting transition and can be described well by an effective two-band model with unbalanced diffusivity, while [Formula: see text] shows a flattening below 35 K and follows the Werthamer-Helfand-Hohenberg (WHH) model incorporating orbital pair-breaking and spin-paramagnetic effects, yielding zero-temperature critical fields of [Formula: see text] T and [Formula: see text] T. The anisotropy of the upper critical fields, [Formula: see text] monotonically decreases with decreasing temperature from about 7 near Tcto 1.5 at 0 K. This reduced anisotropy, observed in most Fe-based superconductors, is caused by the Pauli limitation of [Formula: see text].
authors.affiliation: Hochfeld-Magnetlabor Dresden (HLD-EMFL), Helmholtz-Zentrum Dresden-Rossendorf, D-01314 Dresden, Germany.
authors.forename: Zhaosheng
authors.initials: Z
authors.lastname: Wang
authors.forename: Jie
authors.initials: J
authors.lastname: Yuan
authors.forename: J
authors.initials: J
authors.lastname: Wosnitza
authors.forename: Huaxue
authors.initials: H
authors.lastname: Zhou
authors.forename: Yulong
authors.initials: Y
authors.lastname: Huang
authors.forename: Kui
authors.initials: K
authors.lastname: Jin
authors.forename: Fang
authors.initials: F
authors.lastname: Zhou
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Dong
authors.forename: Zhongxian
authors.initials: Z
authors.lastname: Zhao