ELECTRONIC RAMAN-SCATTERING OF YBA2CU3O7 USING C-AXIS POLARIZATION - EVIDENCE FOR 2 CHARACTERISTIC SUPERCONDUCTING ENERGIES

Raman scattering has been obtained with light polarized along the c axis of twin-free single crystals of YBa2Cu3O7. For c-axis polarization, an electronic continuum is observed, similar to the continuum observed for polarization within the a-b plane. In the superconducting state, there is a small decrease in the intensity of the c-axis continuum at energies below 200 cm-1. This change is not purely thermal in origin, since it occurs at essentially the same energy for temperatures between 4 and 65 K. This behavior differs from the large redistribution that occurs below Tc in the continuum observed for polarization within the a-b plane. If the characteristic energies for c-axis polarization (200 cm-1) and a-b polarization (400500 cm-1) are interpreted as superconducting energy gaps, then there is either a single anisotropic gap or two gaps. © 1990 The American Physical Society.