Superconducting dome with $extended$ $s$-$wave$ pairing symmetry in the heavily hole-overdoped copper-oxide planes

TL;DR

This paper demonstrates that a superconducting dome with extended s-wave symmetry appears in heavily hole-overdoped copper-oxide planes, with the pairing mainly from $d_{3z^2-r^2}$ orbitals, aligning with recent experimental findings.

Contribution

It introduces a two-orbital $t$-$J$-$U$ model showing the emergence of an extended s-wave superconducting dome in heavily hole-overdoped regimes, highlighting the role of $d_{3z^2-r^2}$ orbitals.

Findings

Superconducting dome appears in heavily hole overdoped regime.

Dominant pairing contribution from $d_{3z^2-r^2}$ orbitals.

Lower critical doping coincides with Lifshitz transition.

Abstract

We analyze the two-orbital (with $d_{x^2-y^2}$ and $d_{3z^2-r^2}$ orbitals) analogue of the $t$-$J$-$U$ model as applied to the description of the copper-oxide monolayer deposited on the Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ substrate (CuO$_2$/BSCCO). We show, that an $extended$ $s$-$wave$ superconducting dome appears in the heavily hole overdoped regime of the model, with dominant contribution to the pairing coming from the $d_{3z^2-r^2}$ orbitals. Also, the lower critical doping for the appearance of the SC state concurs with the Lifshitz Transition after which the hole-like Fermi pockets are created around the $M$ points in the Brillouin zone. The obtained results are in accord with the recent experimental result [cf. Y. Zhong et al., Sci. Bull. 61, 1239 (2016)]. An analogous two-band description is also analyzed in the context of the Ba$_2$CuO$_{4-y}$ bulk compound, where the heavily hole-overdoped situation is believed to be reached [cf. W. M. Li et al. PNAS 116, 12156 (2019)]. As we show, a two dome structure can be realized in such system with the $d$- and $s$-$wave$ symmetries of the gap corresponding to the low hole-doping and heavily hole overdoped cases, respectively.