Electronic Phase Separation in Iron Selenide (Li,Fe)OHFeSe Superconductor System

• 来源期刊: 中国物理快报（英文版）
• 年，卷（期）: 2018,（5）
• 页码范围: 123-128
• 页数: 6页
• 语种: 英文
• DOI: 10.1088/0256-307X/35/5/057402

摘要

The phenomenon of phase separation into antiferromagnetic (AFM) and superconducting (SC) or normal-state regions has great implication for the origin of high-temperature (high-Tc) superconductivity.However,the occurrence of an intrinsic antiferromagnetism above the Tc of (Li,Fe)OHFeSe superconductor is questioned.Here we report a systematic study on a series of (Li,Fe)OHFeSe single crystal samples with Tc up to ～41 K.We observe an evident drop in the static magnetization at Tafm ～ 125 K,in some of the SC (Tc (≤) 38 K,cell parameter c (≤) 9.27(A)) and non-SC samples.We verify that this AFM signal is intrinsic to (Li,Fe)OHFeSe.Thus,our observations indicate mesoscopic-to-macroscopic coexistence of an AFM state with the normal (below Tafm) or SC (below To) state in (Li,Fe)OHFeSe.We explain such coexistence by electronic phase separation,similar to that in high-Tc cuprates and iron arsenides.However,such an AFM signal can be absent in some other samples of (Li,Fe)OHFeSe,particularly it is never observed in the SC samples of Tc (≥) 38 K,owing to a spatial scale of the phase separation too small for the macroscopic magnetic probe.For this case,we propose a microscopic electronic phase separation.The occurrence of two-dimensional AFM spin fluctuations below nearly the same temperature as Tafm,reported previously for a (Li,Fe)OHFeSe (Tc ～ 42 K) single crystal,suggests that the microscopic static phase separation reaches vanishing point in high-Tc (Li,Fe)OHFeSe.A complete phase diagram is thus established.Our study provides key information of the underlying physics for high-Tc superconductivity.