Fano electron-phonon effects in the far-infrared properties of high-Tc superconductors

Abstract

We present loss-energy spectra, Im ε -1Ω ), calculated by use Kramers- Kronig transformation to the far-infrared reflectivity spectra of the superconducting YBa2Cu3O7-x, Bi4Sr4CaCu3O14+x, Bi2Sr2CaCu2O8+x a-axis oriented textures in a frequency range 50 - 700 cm-1 at temperatures 20 - 300 K, focusing on the phonon properties in the undoped structures. Fano-like antiresonance minima near 300 cm-1 has been observed in a-axis oriented textures well below Tc and analyzed by Fano configuration interaction theory as result of interference between the B2u (B1g) plane- oxygen mode and low-energy charge continua that arises from electronic excitations on the Fermi surface.