skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Ferro-Lattice-Distortions and Charge Fluctuations in Superconducting LaO 1- x F x BiS 2

Abstract

Competing ferroelectric and charge density wave states have been proposed to exist in the electron–phonon coupled LaO1-xFxBiS2 superconductor. The lattice instability is proposed to arise from unstable phonon modes that can break the crystal symmetry. Using single crystal diffraction, a superlattice pattern is observed, that arises from coherent in-plane displacements of the sulfur atoms in the BiS2 superconducting planes. The distortions morph into coordinated ferrodistortive patterns with displacements in the x- and y-directions, that alternate along the c-axis. Diffuse scattering is observed along the (H0L) plane due to stacking faults but not along the (HH0) plane. The ferro-distortive pattern remains in the superconducting state upon fluorine doping, but the displacements are diminished in magnitude. Moreover, we find that the in-plane distortions give rise to disorder where the (00L) reflections become quite broad. It is possible that charge carriers can get trapped in the lattice deformations reducing the effective number of carriers available for pairing.

Authors:
 [1];  [2];  [3];  [3];  [3];  [4];  [5];  [1]
  1. Department of Physics, University of Virginia, Charlottesville, VA 22904, U.S.A.
  2. Oak Ridge National Laboratory, Oak Ridge, TN 37831, U.S.A.
  3. Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506, U.S.A.
  4. Hefei High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, China
  5. Argonne National Laboratory, Lemont, IL 60439, U.S.A.
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science - Office of Basic Energy Sciences - Scientific User Facilities Division; National Science Foundation (NSF)
OSTI Identifier:
1392439
DOE Contract Number:
AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the Physical Society of Japan; Journal Volume: 86; Journal Issue: 5
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY

Citation Formats

Athauda, Anushika, Hoffmann, Christina, Aswartham, Saicharan, Terzic, Jasminka, Cao, Gang, Zhu, Xiangde, Ren, Yang, and Louca, Despina. Ferro-Lattice-Distortions and Charge Fluctuations in Superconducting LaO 1- x F x BiS 2. United States: N. p., 2017. Web. doi:10.7566/JPSJ.86.054701.
Athauda, Anushika, Hoffmann, Christina, Aswartham, Saicharan, Terzic, Jasminka, Cao, Gang, Zhu, Xiangde, Ren, Yang, & Louca, Despina. Ferro-Lattice-Distortions and Charge Fluctuations in Superconducting LaO 1- x F x BiS 2. United States. doi:10.7566/JPSJ.86.054701.
Athauda, Anushika, Hoffmann, Christina, Aswartham, Saicharan, Terzic, Jasminka, Cao, Gang, Zhu, Xiangde, Ren, Yang, and Louca, Despina. Mon . "Ferro-Lattice-Distortions and Charge Fluctuations in Superconducting LaO 1- x F x BiS 2". United States. doi:10.7566/JPSJ.86.054701.
@article{osti_1392439,
title = {Ferro-Lattice-Distortions and Charge Fluctuations in Superconducting LaO 1- x F x BiS 2},
author = {Athauda, Anushika and Hoffmann, Christina and Aswartham, Saicharan and Terzic, Jasminka and Cao, Gang and Zhu, Xiangde and Ren, Yang and Louca, Despina},
abstractNote = {Competing ferroelectric and charge density wave states have been proposed to exist in the electron–phonon coupled LaO1-xFxBiS2 superconductor. The lattice instability is proposed to arise from unstable phonon modes that can break the crystal symmetry. Using single crystal diffraction, a superlattice pattern is observed, that arises from coherent in-plane displacements of the sulfur atoms in the BiS2 superconducting planes. The distortions morph into coordinated ferrodistortive patterns with displacements in the x- and y-directions, that alternate along the c-axis. Diffuse scattering is observed along the (H0L) plane due to stacking faults but not along the (HH0) plane. The ferro-distortive pattern remains in the superconducting state upon fluorine doping, but the displacements are diminished in magnitude. Moreover, we find that the in-plane distortions give rise to disorder where the (00L) reflections become quite broad. It is possible that charge carriers can get trapped in the lattice deformations reducing the effective number of carriers available for pairing.},
doi = {10.7566/JPSJ.86.054701},
journal = {Journal of the Physical Society of Japan},
number = 5,
volume = 86,
place = {United States},
year = {Mon May 15 00:00:00 EDT 2017},
month = {Mon May 15 00:00:00 EDT 2017}
}
  • The crystal structures of superconducting LaO{sub 1−x}F{sub x}BiS{sub 2} (x∼0.23, 0.46) were determined by single-crystal X-ray diffraction analysis. Their space group was P4/nmm. Distortion of the Bi–S plane changed when the F content was increased from 0.23 to 0.46, and a nearly flat Bi–S plane was formed at x∼0.46. Computational calculations supported this effect of F doping on distortion of Bi–S plane. LaO{sub 1−x}F{sub x}BiS{sub 2} with higher F contents were computationally predicted to be thermodynamically more unstable under ambient pressure. We discussed the bonding, conductivities, and synthetic routes of LaO{sub 1−x}F{sub x}BiS{sub 2}. - Graphical abstract: Distortion of themore » Bi–S plane in LaO{sub 1−x}F{sub x}BiS{sub 2} changed when the F content was increased from 0.23 to 0.46, and a nearly flat Bi–S plane was formed at x∼0.46 with the appearance of superconductivity. - Highlights: • Crystal structure of LaO{sub 1−x}F{sub x}BiS{sub 2} was determined by single-crystal XRD. • Doping amount of F changes the distortion of the Bi–S plane. • Nearly flat Bi–S planes were found in superconductive LaO{sub 1−x}F{sub x}BiS{sub 2} (x∼0.46). • LaO{sub 1−x}F{sub x}BiS{sub 2} with higher F contents was thermodynamically more unstable. • Bonding, superconductivities, and synthetic routes of LaO{sub 1−x}F{sub x}BiS{sub 2} were discussed.« less
  • Cited by 49
  • We report superconducting properties of PrO{sub 1-x}F{sub x}BiS{sub 2} compounds, synthesized by the vacuum encapsulation technique. The synthesized PrO{sub 1-x}F{sub x}BiS{sub 2} (x = 0.1, 0.3, 0.5, 0.7, and 0.9) samples are crystallized in a tetragonal P4/nmm space group. Both transport and DC magnetic susceptibility measurements showed bulk superconductivity below 4 K. The maximum T{sub c} is obtained for x = 0.7 sample. Under applied magnetic field, both T{sub c}{sup onset} and T{sub c} (ρ = 0) decrease to lower temperatures. We estimated highest upper critical field [H{sub c2}(0)] for PrO{sub 0.3}F{sub 0.7}BiS{sub 2} sample to be above 4 T (Tesla). The thermally activated flux flow activation energymore » (U{sub 0}) is estimated 54.63 meV in 0.05 T field for PrO{sub 0.3}F{sub 0.7}BiS{sub 2} sample. Hall measurement results showed that electron charge carriers are the dominating ones in these compounds. Thermoelectric effects (Thermal conductivity and Seebeck coefficient) data suggest strong electron-electron correlations in this material.« less
  • On the basis of the crystal structures of ..beta..-(ET)/sub 2/X (X/sup -/ = IBr/sub 2//sup -/, AuI/sub 2//sup -/, I/sub 3//sup -/) determined at low temperature under ambient and applied pressure, they examined the structural factors responsible for the occurrence of the structural modulation in ..beta..-(ET)/sub 2/I/sub 3/ under ambient pressure, its disappearance under pressure greater than approx. 0.5 kbar, and its effect on the superconducting transition temperature T/sub c/ and the dependence of T/sub c/ on anion X/sup -/ in ..beta..-(ET)/sub 2/X. ET is an abbreviation for BEDT-TTF, i.e., bis(ethylenedithio)tetrathiafulvalene. The electron-phonon coupling constants, lambda, calculated for ..beta..-(ET)/sub 2/Xmore » on the basis of the McMillan equation suggest that the lattice softness with respect to translational and/or librational modes of vibration increases in the order ..beta..-(ET)/sub 2/I/sub 3/ < ..beta..-(ET)/sub 2/IBr/sub 2/ < ..beta..-(ET)/sub 2/AuI/sub 2/ < ..beta..*-(ET)/sub 2/I/sub 3/, where ..beta..*-(ET)/sub 2/I/sub 3/ refers to the ..beta..-(ET)/sub 2/I/sub 3/ salt under an applied pressure greater than approx. 0.5 kbar with T/sub c/ similarly ordered 8 K. They also discuss the importance of hydrogen...anion interactions in understanding the lower T/sub c/ values (1-1.5 K) of the other class of organic superconductors (TMTSF)/sub 2/X (X/sup -/ = ClO/sub 4//sup -/, PF/sub 6//sup -/) compared to the ..beta..-(ET)/sub 2/X systems and the implications concerning the synthesis of new organic superconductors.« less
  • We prepared a series of Mg{sub 1-x}(AlLi){sub x}B{sub 2} samples with 0{<=}x{<=}0.45 in order to compensate with Li the electron doping induced by Al. Structural characterization by means of neutron and x-ray diffraction confirms that Li enters the MgB{sub 2} structure even though in an amount less than nominal one. We performed susceptibility, resistivity, and specific heat measurements. Vibrational properties were also investigated by means of Raman spectroscopy. We compare these results with those obtained on a homologous series of Mg{sub 1-x}Al{sub x}B{sub 2} samples. The systematic success of scaling the relevant properties with the Al content rather than withmore » the electron doping suggests that lattice deformation plays an important role in tuning the superconducting properties.« less