SUPERCONDUCTING GAP ANISOTROPY AND PHONON ANOMALIES IN SINGLE CRYSTAL NDBA2CU3O7-X

摘要

The temperature dependence of the low-frequency part of electronic Raman scattering was investigated in single crystal NdBa2Cu3O7-x with light polarized within the CuO2 planes and along the c axis. From the electronic continuum redistribution below T-c, the pair-breaking energy is derived and is shown to depend on polarization. The in-plane pair-breaking 2 Delta peaks are located at 330 cm(-1) for the A(1g) symmetry and around 580 cm(-1) for B-1g. If we assume that the pair-breaking peak position is a measure of the superconducting gap, these values are almost the same, as in YBa2Cu3O7-x, 2 Delta/T-c ratios being roughly 5.2 and 8.5. For the c-axis response we detect the pair-breaking peak between 400 and 500 cm(-1) and there is also a small decrease in the intensity at frequencies below 200 cm(-1). We also discuss some phonon anomalies probably caused by the substitution of Ba2+ by Nd3+. [References: 17]