Superconducting Phases in Potassium-Intercalated Iron Selenides
arXiv:1302.7178 · doi:10.1021/ja312705x
Abstract
The ubiquitous coexistence of majority insulating 245 phases and minority superconducting (SC) phases in AxFe2-ySe2 (A = K, Cs, Rb, Tl/Rb, Tl/K) formed by high-temperature routes makes pure SC phases highly desirable for studying the intrinsic properties of this SC family. Here we report that there are at least two pure SC phases, KxFe2Se2(NH3)y (x ~ 0.3 and 0.6), determined mainly by potassium concentration in the K-intercalated iron selenides formed via the liquid ammonia route. K0.3Fe2Se2(NH3)0.47 corresponds to the 44 K phase with lattice constant c = 15.56(1) angstroms and K0.6Fe2Se2(NH3)0.37 to the 30 K phase with c = 14.84(1) angstroms. With higher potassium doping, the 44 K phase can be converted into the 30 K phase. NH3 has little, if any, effect on superconductivity. Thus, the conclusions should apply to both K0.3Fe2Se2 and K0.6Fe2Se2 SC phases. K0.3Fe2Se2(NH3)0.47 and K0.6Fe2Se2(NH3)0.37 stand out among known superconductors as their structures are stable only at particular potassium doping levels, and hence the variation of Tc with doping is not dome-like.
4 pages, 4 figures
References in corpus (12)
- Superconductivity at 38 K in the iron arsenide (Ba1-xKx)Fe2As2
- Heavily electron-doped electronic structure and isotropic superconducting gap in AxFe2Se2 (A=K,Cs)
- Fe-based high temperature superconductivity with Tc=31K bordering an insulating antiferromagnet in (Tl,K)FexSe2 Crystals
- Superconductivity at 32 K in single crystal RbFeSe}
- Superconductivity at 32K and anisotropy in Tl0.58Rb0.42Fe1.72Se2 crystals
- NMR Study in the Iron-Selenide Rb0.74Fe1.6Se2: Determination of the Superconducting Phase as Iron Vacancy-Free Rb0.3Fe2Se2
- Phase relations in K_xFe_{2-y}Se_2 and the structure of superconducting K_xFe_2Se_2 via high-resolution synchrotron diffraction
- Superconductivity at Tc = 44 K in LixFe2Se2(NH3)y
- Superconductivity at 44 K in K intercalated FeSe system with excess Fe
- Evolution of precipitate morphology during heat treatment and its implications for the superconductivity in KxFe1.6+ySe2 single crystals
- Overview on the physics and materials of the new superconductor KxFe2-ySe2
- Superconductivity and magnetism in RbxFe2-ySe2: Impact of thermal treatment on mesoscopic phase separation