Novel Electronic State and Superconductivity in the Electron-Doped High-Tc T’-Superconductors
1
Department of Engineering and Applied Sciences, Sophia University, Tokyo 102-8554, Japan
2
Department of Applied Physics, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan
*
Author to whom correspondence should be addressed.
Condens. Matter 2017, 2(3), 23; https://doi.org/10.3390/condmat2030023
Received: 28 April 2017
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Revised: 27 June 2017
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Accepted: 27 June 2017
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Published: 4 July 2017
(This article belongs to the Special Issue Layered Superconductors)
In this review article, we show our recent results relating to the undoped (Ce-free) superconductivity in the electron-doped high- cuprates with the so-called T’ structure. For an introduction, we briefly mention the characteristics of the electron-doped T’-cuprates, including the reduction annealing, conventional phase diagram and undoped superconductivity. Then, our transport and magnetic results and results relating to the superconducting pairing symmetry of the undoped and underdoped T’-cuprates are shown. Collaborating spectroscopic and nuclear magnetic resonance results are also shown briefly. It has been found that, through the reduction annealing, a strongly localized state of carriers accompanied by an antiferromagnetic pseudogap in the as-grown samples changes to a metallic and superconducting state with a short-range magnetic order in the reduced superconducting samples. The formation of the short-range magnetic order due to a very small amount of excess oxygen in the reduced superconducting samples suggests that the T’-cuprates exhibiting the undoped superconductivity in the parent compounds are regarded as strongly correlated electron systems, as well as the hole-doped high- cuprates. We show our proposed electronic structure model to understand the undoped superconductivity. Finally, unsolved future issues of the T’-cuprates are discussed.
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Keywords:
electron-doped high-Tc cuprate; undoped (Ce-free) superconductivity; reduction annealing; transport property; muon spin relaxation; novel electronic structure model
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MDPI and ACS Style
Adachi, T.; Kawamata, T.; Koike, Y. Novel Electronic State and Superconductivity in the Electron-Doped High-Tc T’-Superconductors. Condens. Matter 2017, 2, 23. https://doi.org/10.3390/condmat2030023
AMA Style
Adachi T, Kawamata T, Koike Y. Novel Electronic State and Superconductivity in the Electron-Doped High-Tc T’-Superconductors. Condensed Matter. 2017; 2(3):23. https://doi.org/10.3390/condmat2030023
Chicago/Turabian StyleAdachi, Tadashi, Takayuki Kawamata, and Yoji Koike. 2017. "Novel Electronic State and Superconductivity in the Electron-Doped High-Tc T’-Superconductors" Condensed Matter 2, no. 3: 23. https://doi.org/10.3390/condmat2030023
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