Momentum
Dependence of Fluctuation Spectrum of Slightly Underdoped Bi2Sr2CaCu2O2+¥ä
from High Resolution Laser ARPES
Han-Yong Choi, Sungkyunkwan University
The
Eliashberg function describes the spectral function of the fluctuation and
their coupling to electrons and is therefore of fundamental importance in
determining the normal state properties and pairing mechanism in metals. For
conventional superconductors it was successfully extracted by the
McMillan-Rowell procedure. For the cuprates, however, its momentum dependence
has not yet been determined directly from experimental data. Here, we report
the deduction of momentum dependence of Eliashberg function ¥á2F(¥è,¥ø)
at energy ¥ø and along momentum cuts at angles ¥è normal to the Fermi
surface from the high resolution laser angle resolved photoemission
spectroscopy on slightly underdoped Bi2Sr2CaCu2O2+¥ä
in normal state. Our principle result is that despite the ¥è dependence of the
single-particle self-energy, the ¥á2F(¥è,¥ø) collapse onto a single
function of ¥ø independent of ¥è. It has a weak peak around 0.05 eV and an
intrinsic cut-off of about 0.4 eV or the energy of the band bottom in direction
¥è, whichever is lower. These results are consistent only with fluctuation
spectra which have the correlation length of the lattice constant or shorter.