Orbital Symmetry and Orbital Excitations in High-\(T_c\) Superconductors

We discuss a few possibilities of high-\(T_c\) superconductivity with more than one orbital symmetry contributing to the pairing. First, we show that the high energies of orbital excitations in various cuprates suggest a simplified model with a single orbital of \(x^2-y^2\) symmetry doped by holes....

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Bibliographic Details
Published in:arXiv.org 2019-05
Main Authors: Oleś, Andrzej M, Wohlfeld, Krzysztof, Khaliullin, Giniyat
Format: Article
Language:English
Subjects:
Barium
Cuprates
Electron spin
Electrons
Entangled states
Excitation
Group 5A compounds
Heterostructures
Strontium
Superconductivity
Symmetry
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Summary:We discuss a few possibilities of high-\(T_c\) superconductivity with more than one orbital symmetry contributing to the pairing. First, we show that the high energies of orbital excitations in various cuprates suggest a simplified model with a single orbital of \(x^2-y^2\) symmetry doped by holes. Next, several routes towards involving both \(e_g\) orbital symmetries for doped holes are discussed: (i) some give superconductivity in a CuO\(_2\) monolayer on Bi2212 superconductors, Sr\(_2\)CuO\(_{4-\delta}\), Ba\(_2\)CuO\(_{4-\delta}\), while (ii) others as nickelate heterostructures or Eu\(_{2-x}\)Sr\(_x\)NiO\(_4\), could in principle realize it as well. At low electron filling of Ru ions, spin-orbital entangled states of \(t_{2g}\) symmetry contribute in Sr\(_2\)RuO\(_4\). Finally, electrons with both \(t_{2g}\) and \(e_g\) orbital symmetries contribute to the superconducting properties and nematicity of Fe-based superconductors, pnictides or FeSe. Some of them provide examples of orbital-selective Cooper pairing.
ISSN:2331-8422
DOI:10.48550/arxiv.1905.02594