An approach for studying the influence of uniaxial strain (pressure) on the temperature of the Bose-Einstein condensation of intersite bipolarons: possible implementation for RBa${}_2$Cu${}_3$O${}_{7-\delta }$ cuprates

A universal approach is proposed to study the influence of strain (pressure) on the temperature of Bose-Einstein condensation of intersite bipolarons within the extended Holstein model. It is shown that uniaxial strain (pressure) derivatives of the temperature of such a Bose-Einstein condensation strongly depend on the arrangement of ions in the lattice. In particular, they may be positive or negative. A connection between the theoretically obtained results, along with the experimental data, on the influence of uniaxial pressure (strain) on $T_c$ of RBa${}_2$Cu${}_3$O${}_{7-\delta }$ family cuprates is discussed.