Role of the 245 phase in alkaline iron selenide superconductors revealed by high-pressure studies
Peiwen Gao, Rong Yu, Liling Sun, Hangdong Wang, Zhen Wang, Qi Wu, Minghu Fang, Genfu Chen, Jing Guo, Chao Zhang, Dachun Gu, Huanfang Tian, Jianqi Li, Jing Liu, Yanchun Li, Xiaodong Li, Sheng Jiang, Ke Yang, Aiguo Li, Qimiao Si, Zhongxian Zhao
DOI 10.1103/PhysRevB.89.094514 · Physical Review B
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Abstract
There is considerable interest in uncovering the physics of iron-based superconductivity from the alkaline iron selenides, a materials class containing an insulating phase (245 phase) and a superconducting (SC) phase. Due to the microstructural complexity of these superconductors, the role of the 245 phase in the development of the superconductivity has been a puzzle. Here we demonstrate a comprehensive high-pressure study on the insulating samples with pure 245 phase and biphasic SC samples. We find that the insulating behavior can be completely suppressed by pressure in the insulating samples and also identify an intermediate metallic (M′) state. The Mott insulating (MI) state of the 245 phase and the M′ state coexist over a significant range of pressure up to ∼10 GPa, the same pressure at which the superconductivity of the SC samples vanishes. Our results reveal the M′ state as a pathway that connects the insulating and SC phases of the alkaline iron selenides and indicate that the coexistence and interplay between the MI and M′ states is a necessary condition for superconductivity. Finally, we interpret the M′ state in terms of an orbital selectivity of the correlated 3d electrons.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| Tl0.4Rb0.4Fe1.67Se2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 32 | Pressure unresolved | unknown |
| K0.8Fe1.70Se2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 32 | Pressure unresolved | unknown |
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