Microscopic studies of the optical spectra of ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ have been done using the linear-muffin-tin-orbital (LMTO) method for solving the band-structure problem. Special attention has been paid to the midinfrared and visible spectral range where a number of peculiarities including the large anisotropy of the optical reflectance was observed. It is shown that the overall features of the observed optical spectra can be well explained in the framework of the usual band-structure approach. Moreover, the anisotropy of the reflectance in the a-b planes and the positions of the main interband transitions are also in good agreement with available experimental data.

• Received 21 July 1989

DOI:https://doi.org/10.1103/PhysRevLett.63.1880