Effect of Mn substitution on superconductivity in iron selenide (Li, Fe)OHFeSe single crystals

We synthesize a series of Mn substituted (Li, Fe)OHFeSe superconductor single crystals via a modified ion-exchange method, with the Mn dopant concentration z (the atomic ratio of Mn:Se) ranging from zero to 0.07. Interestingly, we find that the superconducting transition temperature T_c and unit cell parameter c of the Mn-doped (Li, Fe)OHFeSe samples display similar V-shaped evolutions with the dopant concentration z. The Mn dopant may be accommodated in the tetrahedral sites of both the (Li, Fe)OH- and FeSe-layers depending on the doping level, leading to a reduced or enhanced interlayer separation of (Li, Fe)OHFeSe. The observed positive correlation between the T_c and lattice parameter c, regardless of the Mn doping level z, indicates that a larger interlayer separation, or a weaker interlayer coupling, is essential for the high-T_c superconductivity in (Li, Fe)OHFeSe.
Corresponding authors: dong@iphy.ac.cn, zhxzhao@iphy.ac.cn
References
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