The effect of $c$-axis compression on the electronic structure and superconducting (SC) properties of the high-temperature SC cuprate ${\mathrm{La}}_{2-x}{\mathrm{Sr}}_x{\mathrm{CuO}}_4$ at different doping levels is investigated. The electronic structure of quasiparticle excitations is obtained within the effective five-band Hubbard model, using the equation of motion method for Green's functions based on Hubbard operators. The SC gap and $T_c$ are calculated by considering the exchange pairing mechanism, which involves not only the Zhang-Rice singlet but also excited two-hole triplet and singlet states. The energy of the $a_{1g}$ orbitals increases with increasing compression, and the $a_{1g}$ quasiparticle bands begin to strongly interact with the $b_{1g}$ bands at the top of the valence band. The reconstruction of the region of states that determine the SC properties results in a high density of states near the Fermi level. This mechanism leads to an increase in $T_c$ in the underdoped region with increasing compression. On the other hand, the renormalization of the pairing constants under compression results in a decrease in $T_c$. The competition between these two effects leads to the nonmonotonic behavior of $T_c$ under $c$-axis compression near optimal doping.

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• Pressure effects
• Spin-singlet pairing
• Superconducting gap
• Superconductivity
• High-temperature superconductors
• Strongly correlated systems
• Green's function methods
• Hubbard model
• Methods in superconductivity