Strain effect on the high T c superconductor YBa2Cu3O7: an ab initio study comparing bulk and monolayer models

In this work, the effect of strain on the vibrational and electronic properties of the YBa2Cu3O7 compound was studied through ab initio calculations. For this, two structural models were used: a bulk model and a surface model (a monolayer with CuO2 and BaO as the terminating layers). The phonon spectra was calculated for both structures under different levels of c axis strain. The most appreciable change occurs in the vibrational properties, and in the surface case. From the simulation of the Raman spectra, we were able to quantify the Raman shift ratio as a function of the applied strain, and analyzed its behavior in terms of the overlap population of the different bonds and the reduced mass of selected phonons. The effect of the level of deformation on the band structure and the electronic density of states is small for both structures, although more noticeable in the case of the surface model. In both cases, tendencies are observed when the fine features of the band structure are analyzed by means of the tight binding model. Due to the lower symmetry, the surface model also shows modifications of the bands related to the CuO2 planes.

Automated summary

The effect of strain on the vibrational and electronic properties of YBa2Cu3O7 compound was studied using ab initio calculations. Two structural models, a bulk model and a surface model, were employed to investigate the phonon spectra under varying levels of c axis strain. The most significant changes were observed in the vibrational properties, particularly in the surface model. Raman spectra simulations allowed for the quantification of the Raman shift ratio and its analysis in terms of bond overlap population and phonon mass reduction, revealing tendencies in the fine features of the band structure in both models.