Ferro-lattice-distortions and charge fluctuations in superconducting LaO${}_{1-x}$F${}_x$BiS${}_2$

Abstract

Competing ferroelectric and charge density wave phases have been proposed to be present in the electron-phonon coupled LaO${}_{1-x}$F${}_x$BiS${}_2$ superconductor. The lattice instability arises from unstable phonon modes that can break the crystal symmetry. Upon examination of the crystal structure using single crystal diffraction, we find a superlattice pattern arising from coherent in-plane displacements of the sulfur atoms in the BiS${}_2$ superconducting planes. The distortions morph into coordinated ferro-distortive patterns, challenging previous symmetry suggestions including the possible presence of unstable antiferro-distortive patterns. The ferro-distortive pattern remains in the superconducting state, but with the displacements diminished in magnitude. Moreover, the sulfur displacements can exist in several polytypes stacked along the c-axis. Charge carriers can get trapped in the lattice deformations reducing the effective number of carriers available for pairing.

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• Ferroelectric Soft Phonons, Charge Density Wave Instability and Strong Electron-Phonon Coupling in BiS2-Layered Superconductors
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• In-plane Charge Fluctuations in Bismuth Sulfide Superconductors
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Cited by in corpus (7)

• Material Development and Physical Properties of BiS2-Based Layered Compounds
• SnAs-based layered superconductor NaSn2As2
• Charge Fluctuations in the NdO${}_{1-x}$F${}_x$BiS${}_2$ Superconductors
• Direct Observation of an Incommensurate Charge Density Wave in the BiS2-based Superconductor NdO1-xFxBiS2
• Pressure-induced superconductivity in layered pnictogen diselenide NdO${}_{0.8}$F${}_{0.2}$Sb${}_{1-x}$Bi${}_x$Se${}_2$ (x = 0.3 and 0.7)
• Pressure-induced enhancement of two-dimensionality in LaO1-xFxBi(Se/S)2 superconductors
• Crystal Structure and Thermoelectric Transport Properties of As-Doped Layered Pnictogen Oxyselenides NdO0.8F0.2Sb1-xAsxSe2