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

Title: Final Technical Report for DE-FG02-86ER45268

Abstract

This work addresses several key issues for understanding the unusual superconductivity in IBS, already shown to be technologically useful materials. 1a). Are reactive gasses like fluorine, chlorine, or water vapor behaving simply as electron donors to cause the superconductivity (at T conset=21 K) in undoped IBS like BaFe 2As 2? 1b). Does exposure to fluorine increase T c in electron-doped IBS materials that are underdoped, e. g. Ba(Fe 0.96Co 0.04) 2As 2? 1c). Can fluorine as a reactive electron-donor, with its relatively greater ease of introduction into the lattice, be used as a rapid tool to search for superconductivity in new materials under investigation? Method of investigation: Using electron probe microanalysis, x-ray photoemission spectroscopy, and dynamical mean field theory calculations, we found that fluorine substitutes for As in the BaFe 2As 2 lattice, and should therefore behave as an electron donor. We will F-dope Ba(Fe 0.96Co 0.04) 2As 2 and several new compounds under investigation for superconductivity upon doping to determine fluorine’s effect. Potential impact: If – like for fluorine - a brief exposure to hydrogen indeed causes superconductivity to a depth of 10 microns, this technique could be useful in creating long lengths of superconducting tape without the chemicalmore » aggressiveness of fluorine. Using the F ion, which substitutes for As - away from the Fe planes, in underdoped IBS like Ba(Fe 0.96Co 0.04) 2As 2 may form optimally doped IBS with less impurity scattering of the superconducting Fe 3d electrons resulting in improved superconducting properties. Another potential impact is the speed of checking for superconductivity in new materials under investigation for superconductivity upon doping. 2. What are the effects of Be substitution into IBS, beginning with FeSe and its derivatives (FeSe 1-xS x and FeSe 1-xTe x) and BaFe 2-xCo xAs 2? Method of investigation: We recently succeeded in adding Be to the FeSe lattice and found, surprisingly, a factor of four improvement of the low temperature residual resistivity ratio, consistent with improved electronic ordering. Using single crystal x-ray diffraction and x-ray dispersive spectroscopy, determine the concentration and location of the Be dopant. Using resistivity, determine if there is improvement in the residual resistivity achieved by Be doping in the FeSe derivatives (using AlCl 3:KCl flux growth) and Co-doped BaFe 2As 2 (using self-flux single crystal growth). Measuring resistivity under strain, determine the changes of the nematic susceptibility at the structural ordering transition causes by the increase in electronic order caused by Be doping in FeSe. Potential impact: Further understanding of IBS, including FeSe which - under physical pressure - has a T c increase to 40 K and -prepared as a monolayer - has a T c reported to be over 100 K. 3. In collaboration, prepare light atom compounds involving Be and look for high pressure-induced superconductivity.« less

Authors:
ORCiD logo [1]
  1. University of Florida
Publication Date:
Research Org.:
G. R. Stewart/University of Florida
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1598468
Report Number(s):
DOE_GRStewart_UnivFlorida_45268
DOE Contract Number:  
FG02-86ER45268
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; superconductivity, iron based, specific heat

Citation Formats

Stewart, G. R. Final Technical Report for DE-FG02-86ER45268. United States: N. p., 2020. Web. doi:10.2172/1598468.
Stewart, G. R. Final Technical Report for DE-FG02-86ER45268. United States. doi:10.2172/1598468.
Stewart, G. R. Sun . "Final Technical Report for DE-FG02-86ER45268". United States. doi:10.2172/1598468. https://www.osti.gov/servlets/purl/1598468.
@article{osti_1598468,
title = {Final Technical Report for DE-FG02-86ER45268},
author = {Stewart, G. R.},
abstractNote = {This work addresses several key issues for understanding the unusual superconductivity in IBS, already shown to be technologically useful materials. 1a). Are reactive gasses like fluorine, chlorine, or water vapor behaving simply as electron donors to cause the superconductivity (at Tconset=21 K) in undoped IBS like BaFe2As2? 1b). Does exposure to fluorine increase Tc in electron-doped IBS materials that are underdoped, e. g. Ba(Fe0.96Co0.04)2As2? 1c). Can fluorine as a reactive electron-donor, with its relatively greater ease of introduction into the lattice, be used as a rapid tool to search for superconductivity in new materials under investigation? Method of investigation: Using electron probe microanalysis, x-ray photoemission spectroscopy, and dynamical mean field theory calculations, we found that fluorine substitutes for As in the BaFe2As2 lattice, and should therefore behave as an electron donor. We will F-dope Ba(Fe0.96Co0.04)2As2 and several new compounds under investigation for superconductivity upon doping to determine fluorine’s effect. Potential impact: If – like for fluorine - a brief exposure to hydrogen indeed causes superconductivity to a depth of 10 microns, this technique could be useful in creating long lengths of superconducting tape without the chemical aggressiveness of fluorine. Using the F ion, which substitutes for As - away from the Fe planes, in underdoped IBS like Ba(Fe0.96Co0.04)2As2 may form optimally doped IBS with less impurity scattering of the superconducting Fe 3d electrons resulting in improved superconducting properties. Another potential impact is the speed of checking for superconductivity in new materials under investigation for superconductivity upon doping. 2. What are the effects of Be substitution into IBS, beginning with FeSe and its derivatives (FeSe1-xSx and FeSe1-xTex) and BaFe2-xCoxAs2? Method of investigation: We recently succeeded in adding Be to the FeSe lattice and found, surprisingly, a factor of four improvement of the low temperature residual resistivity ratio, consistent with improved electronic ordering. Using single crystal x-ray diffraction and x-ray dispersive spectroscopy, determine the concentration and location of the Be dopant. Using resistivity, determine if there is improvement in the residual resistivity achieved by Be doping in the FeSe derivatives (using AlCl3:KCl flux growth) and Co-doped BaFe2As2 (using self-flux single crystal growth). Measuring resistivity under strain, determine the changes of the nematic susceptibility at the structural ordering transition causes by the increase in electronic order caused by Be doping in FeSe. Potential impact: Further understanding of IBS, including FeSe which - under physical pressure - has a Tc increase to 40 K and -prepared as a monolayer - has a Tc reported to be over 100 K. 3. In collaboration, prepare light atom compounds involving Be and look for high pressure-induced superconductivity.},
doi = {10.2172/1598468},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2020},
month = {2}
}

Works referenced in this record:

Superconductivity in a unique type of copper oxide
journal, May 2019

  • Li, W. M.; Zhao, J. F.; Cao, L. P.
  • Proceedings of the National Academy of Sciences, Vol. 116, Issue 25
  • DOI: 10.1073/pnas.1900908116