Experimental and theoretical Raman study on the HTSC PrxY1−xBa2

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

“…In section 3.2.1, we mention that the off-resonant Raman spectrum simulation presents a similar shape to experimental measurements [23,35,50,76,77] and previous theoretical reports [78][79][80].…”

“…Figure 4 shows the off-resonant Raman spectrum simulation for each level of strain. The shape of the spectrum is similar to experimental measurements [50,76,77] and previous theoretical reports [78][79][80]. The frequency modes and their mode assignment are presented in table 2.…”

“…The underlined modes are the only Raman active modes, being the A g modes the ones with highest Raman intensity. Therefore, as in our previous work [50], we expect to obtain five eigenvectors with A g symmetry: Ba z (∼110 cm −1 ) and Cu(2) z (140-145 cm −1 ) atoms displacements, O(3)/O(2) atoms displacements in the CuO 2 planes: out-of-phase (∼335 cm −1 ) and in-phase (∼440 cm −1 ). Finally, the O(4) z displacement in the Ba plane (490-500 cm −1 ); all of them along the z axis (crystallographic c axis).…”

“…A strong Coulombic interaction is included, following the Dudarev et al [49] approach, setting a U eff = U − J of 5.0 eV on the Cu 3d-orbitals to better describe the Cu-d states (electronic localization and correlation). The U eff value was determined in a previous work [50]. This consideration is important when describing highly correlated systems.…”

“…For both the bulk and the slab structures, the following structural optimization procedure was carried out (typically used in orthorhombic systems). Taking the YBCO structure reported in our previous work of ab initio calculations [50] as a starting point, we generated a series of unit cells with different volumes, maintaining the same c/a and b/a ratios. The volumes were varied in the range −5% to +5% with respect to the original cell.…”