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Suppression of spin-exciton state in hole overdoped iron-based superconductors

The mechanism of Cooper pair formation in iron-based superconductors remains a controversial topic. The main question is whether spin or orbital fluctuations are responsible for the pairing mechanism. To solve this problem, a crucial clue can be obtained by examining the remarkable enhancement of ma...

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Autores principales: Lee, C. H., Kihou, K., Park, J. T., Horigane, K., Fujita, K., Waßer, F., Qureshi, N., Sidis, Y., Akimitsu, J., Braden, M.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Nature Publishing Group 2016
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4804212/
https://www.ncbi.nlm.nih.gov/pubmed/27005481
http://dx.doi.org/10.1038/srep23424
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author Lee, C. H.
Kihou, K.
Park, J. T.
Horigane, K.
Fujita, K.
Waßer, F.
Qureshi, N.
Sidis, Y.
Akimitsu, J.
Braden, M.
author_facet Lee, C. H.
Kihou, K.
Park, J. T.
Horigane, K.
Fujita, K.
Waßer, F.
Qureshi, N.
Sidis, Y.
Akimitsu, J.
Braden, M.
author_sort Lee, C. H.
collection PubMed
description The mechanism of Cooper pair formation in iron-based superconductors remains a controversial topic. The main question is whether spin or orbital fluctuations are responsible for the pairing mechanism. To solve this problem, a crucial clue can be obtained by examining the remarkable enhancement of magnetic neutron scattering signals appearing in a superconducting phase. The enhancement is called spin resonance for a spin fluctuation model, in which their energy is restricted below twice the superconducting gap value (2Δ(s)), whereas larger energies are possible in other models such as an orbital fluctuation model. Here we report the doping dependence of low-energy magnetic excitation spectra in Ba(1−x)K(x)Fe(2)As(2) for 0.5 < x < 0.84 studied by inelastic neutron scattering. We find that the behavior of the spin resonance dramatically changes from optimum to overdoped regions. Strong resonance peaks are observed clearly below 2Δ(s) in the optimum doping region, while they are absent in the overdoped region. Instead, there is a transfer of spectral weight from energies below 2Δ(s) to higher energies, peaking at values of 3Δ(s) for x = 0.84. These results suggest a reduced impact of magnetism on Cooper pair formation in the overdoped region.
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spelling pubmed-48042122016-03-23 Suppression of spin-exciton state in hole overdoped iron-based superconductors Lee, C. H. Kihou, K. Park, J. T. Horigane, K. Fujita, K. Waßer, F. Qureshi, N. Sidis, Y. Akimitsu, J. Braden, M. Sci Rep Article The mechanism of Cooper pair formation in iron-based superconductors remains a controversial topic. The main question is whether spin or orbital fluctuations are responsible for the pairing mechanism. To solve this problem, a crucial clue can be obtained by examining the remarkable enhancement of magnetic neutron scattering signals appearing in a superconducting phase. The enhancement is called spin resonance for a spin fluctuation model, in which their energy is restricted below twice the superconducting gap value (2Δ(s)), whereas larger energies are possible in other models such as an orbital fluctuation model. Here we report the doping dependence of low-energy magnetic excitation spectra in Ba(1−x)K(x)Fe(2)As(2) for 0.5 < x < 0.84 studied by inelastic neutron scattering. We find that the behavior of the spin resonance dramatically changes from optimum to overdoped regions. Strong resonance peaks are observed clearly below 2Δ(s) in the optimum doping region, while they are absent in the overdoped region. Instead, there is a transfer of spectral weight from energies below 2Δ(s) to higher energies, peaking at values of 3Δ(s) for x = 0.84. These results suggest a reduced impact of magnetism on Cooper pair formation in the overdoped region. Nature Publishing Group 2016-03-23 /pmc/articles/PMC4804212/ /pubmed/27005481 http://dx.doi.org/10.1038/srep23424 Text en Copyright © 2016, Macmillan Publishers Limited http://creativecommons.org/licenses/by/4.0/ This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/
spellingShingle Article
Lee, C. H.
Kihou, K.
Park, J. T.
Horigane, K.
Fujita, K.
Waßer, F.
Qureshi, N.
Sidis, Y.
Akimitsu, J.
Braden, M.
Suppression of spin-exciton state in hole overdoped iron-based superconductors
title Suppression of spin-exciton state in hole overdoped iron-based superconductors
title_full Suppression of spin-exciton state in hole overdoped iron-based superconductors
title_fullStr Suppression of spin-exciton state in hole overdoped iron-based superconductors
title_full_unstemmed Suppression of spin-exciton state in hole overdoped iron-based superconductors
title_short Suppression of spin-exciton state in hole overdoped iron-based superconductors
title_sort suppression of spin-exciton state in hole overdoped iron-based superconductors
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4804212/
https://www.ncbi.nlm.nih.gov/pubmed/27005481
http://dx.doi.org/10.1038/srep23424
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