Anomalous Eu Valence State and Superconductivity in Undoped Eu3Bi2S4F4

Abstract

We have synthesized a novel europium bismuth sulfofluoride, Eu3Bi2S4F4, by solid-state reactions in sealed evacuated quartz ampoules. The compound crystallizes in a tetragonal lattice (space group I4/mmm, a = 4.0771(1) A, c = 32.4330(6) A, and Z = 2), in which CaF2-type Eu3F4 layers and NaCl-like BiS2 bilayers stack alternately along the crystallographic c axis. There are two crystallographically distinct Eu sites, Eu(1) and Eu(2) at the Wyckoff positions 4e and 2a, respectively. Our bond-valence-sum calculation, based on the refined structural data, indicates that Eu(1) is essentially divalent, whilst Eu(2) has an average valence of +2.64(5). This anomalous Eu valence state is further confirmed and supported, respectively, by Mossbauer and magnetization measurements. The Eu3+ components donate electrons into the conduction bands that are mainly composed of Bi- 6px and 6py states. Consequently, the material itself shows metallic conduction, and superconducts at 1.5 K without extrinsic chemical doping.

24 pages, 5 figures

References in corpus (12)

• Thorium-doping induced superconductivity up to 56 K in Gd1-xThxFeAsO
• Superconductivity Appears in the Vicinity of an Insulating-Like Behavior in CeO${}_{1-x}$F${}_x$BiS${}_2$
• Minimal electronic models for superconducting BiS${}_2$ layers
• Superconductivity of F-substituted LnOBiS2 (Ln = La, Ce, Pr, Nd, Yb) compounds
• Ferroelectric Soft Phonons, Charge Density Wave Instability and Strong Electron-Phonon Coupling in BiS2-Layered Superconductors
• Superconductivity induced by La doping in Sr1-xLaxFBiS2 system
• Pressure Study of BiS2-Based Superconductors Bi4O4S3 and La(O,F)BiS2
• Charge-density wave, superconductivity and $f$-electron valence instability in EuBiS${}_2$F
• RPA Analysis of a Two-orbital Model for the BiS2-based Superconductors
• Self doping effect and successive magnetic transitions in superconducting Sr${}_2$VFeAsO${}_3$
• Optical study of archetypical valence-fluctuating Eu-systems
• Hydrostatic Pressure Studies on Parent Phase SrFBiS2 of BiS2-based Superconducting Family

Cited by in corpus (14)

• Superconductivity in KCa${}_2$Fe${}_4$As${}_4$F${}_2$ with Separate Double Fe${}_2$As${}_2$ Layers
• Pressure-enhanced superconductivity in Eu${}_3$Bi${}_2$S${}_4$F${}_4$
• Superconductivity in CeOBiS2 with cerium valence fluctuation
• Unusual mixed valence of Eu in two new materials EuSr2Bi2S4F4 and Eu2SrBi2S4F4: Mössbauer and X-ray photoemission Spectroscopy investigations
• Superconductivity in Bi3O2S2Cl with Bi-Cl Planar Layers
• Crystal structure, site selectivity, and electronic structure of layered chalcogenide LaOBiPbS3
• Synthesis, Crystal Structure, and Physical Properties of New Layered Oxychalcogenide La2O2Bi3AgS6
• High pressure effects on non-fluorinated BiS2-based superconductors La${}_{1-x}$M${}_x$OBiS${}_2$ (M = Ti and Th)
• Observation of supermodulation in LaO0.5F0.5BiSe2 by scanning tunneling microscopy and spectroscopy
• Growth and characterization of (La,Ce)OBiS2 single crystals
• Growth and superconducting properties of Cd-doped La(O,F)BiS2 single crystals
• Pressure-induced enhancement of the superconducting transition temperature in La2O2Bi3AgS6
• Ultrasonic investigation of the Kondo semimetal CeBi
• Orientation-dependent superconductivity and electronic structure of the rare-earth metal/KTaO3 interfaces