  A first Fermi surface map of a single-layer high-Tc superconductor is
presented. The experiments were carried out on optimally doped
Bi_2Sr_(2-x)La_xCuO_(6+delta)(x=0.40) with synchrotron radiation which allow to
discuss in detail the strong polarisation dependence of the emissions near the
Fermi edge. For the cuprates only little is known about the impact of the
electron-photon matrix element determining the photoelectron intensity. For the
example of the model layered superconductor Bi_2Sr_(2-x)La_xCuO_(6+delta)it
will be demonstrated that the polarization geometry has significant influence
on the energy distribution curves at EF and consequently also for the
determination of the topology and character of the Fermi surface (FS) by
angle-resolved photoemission. For further clarification also a FS map of the
n=2 material Bi-2212 has been measured applying a different polarisation
geometry as previously used by Saini et al.. In the context of the current
debate on the character of the Fermi surface of Bi-cuprates our results confirm
a hole-like Fermi surface for n=1 as well as n=2 material, what might be the
universal FS for high-Tc superconductors.
