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Orbital Symmetry and Orbital Excitations in High-Tc Superconductors

1
Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
2
Marian Smoluchowski Institute of Physics, Jagiellonian University, Prof. S. ojasiewicza 11, PL-30348 Kraków, Poland
3
Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, Pasteura 5, PL-02093 Warsaw, Poland
*
Author to whom correspondence should be addressed.
Condens. Matter 2019, 4(2), 46; https://doi.org/10.3390/condmat4020046
Received: 12 March 2019 / Revised: 29 April 2019 / Accepted: 2 May 2019 / Published: 6 May 2019
(This article belongs to the Special Issue From cuprates to Room Temperature 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. 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 δ , Ba 2 CuO 4 δ , 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 2 g symmetry contribute in Sr 2 RuO 4 . Finally, electrons with both t 2 g 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. View Full-Text
Keywords: high-Tc superconductivity; orbital symmetry; orbital excitation; charge-transfer insulator; Fermi surface; spin-orbit coupling; spin-orbital entanglement; electron-phonon; Cooper pairing high-Tc superconductivity; orbital symmetry; orbital excitation; charge-transfer insulator; Fermi surface; spin-orbit coupling; spin-orbital entanglement; electron-phonon; Cooper pairing
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MDPI and ACS Style

Oleś, A.M.; Wohlfeld, K.; Khaliullin, G. Orbital Symmetry and Orbital Excitations in High-Tc Superconductors. Condens. Matter 2019, 4, 46.

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