Fine Details of the Nodal Electronic Excitations in Bi 2 Sr 2 CaCu 2 O 8+δ
T. Valla, T. E. Kidd, J. D. Rameau, H.-J. Noh, G. D. Gu, P. D. Johnson, H.-B. Yang, H. Ding
Abstract
Very high energy resolution photoemission experiments on high quality samples of optimally doped Bi
2
Sr
2
CaCu
2
O
8+δ
show new features in the low-energy electronic excitations. A marked change in the binding energy and temperature dependence of the near-nodal scattering rates is observed near the superconducting transition temperature,
T
C
. The temperature slope of the scattering rate measured at low energy shows a discontinuity at ~
T
C
. In the superconducting state, coherent excitations are found with the scattering rates showing a cubic dependence on frequency and temperature. The superconducting gap has a d-wave magnitude with negligible contribution from higher harmonics. Further, the bi-layer splitting has been found to be finite at the nodal point.