Orbital Symmetry and Orbital Excitations in High-$T_c$ Superconductors

Andrzej M. Oleś; Krzysztof Wohlfeld; Giniyat Khaliullin

doi:10.3390/condmat4020046

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arXiv · 1905.02594

Orbital Symmetry and Orbital Excitations in High-$T_c$ Superconductors

Andrzej M. Oleś·Krzysztof Wohlfeld·Giniyat Khaliullin

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Abstract

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.

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Andrzej M. Oleś, Krzysztof Wohlfeld, Giniyat Khaliullin. 2019-05-07. Orbital Symmetry and Orbital Excitations in High-$T_c$ Superconductors. https://doi.org/10.3390/condmat4020046

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