20 research outputs found
Coupling to a phononic mode in : Angle-resolved photoemission
The kink in the dispersion and the drop in the width observed by
angle-resolved photoemission in the nodal direction of the Brillouin zone of
(abbreviated as (Pb)Bi2212) has
attracted broad interest [1-3]. Surprisingly optimally lead-doped (Pb)Bi2212
with as well as the shadow band were not investigated so
far, although the origin of the kink and the drop is still under strong debate.
In this context a resonant magnetic-mode scenario and an electron-phonon
coupling scenario are discussed controversially. Here we analyze the relevant
differences between both scenarios and conclude that the kink and the drop are
caused by a coupling of the electronic system to a phononic mode at least in
the nodal direction. It is found that besides the dispersion and the drop in
the width also the peak height as a new criterion can be used to define the
energy scale of the interaction, giving a new means for a precise and
consistent determination of the kink energy
Systematic X-ray absorption study of hole doping in BSCCO - phases
X-ray absorption spectroscopy (XAS) on the O 1s threshold was applied to
Bi-based, single crystalline high temperature superconductors (HTc's), whose
hole densities in the CuO2 planes was varied by different methods. XAS gives
the intensity of the so-called pre-peak of the O 1s line due to the unoccupied
part of the Zhang-Rice (ZR) singlet state. The effects of variation of the
number n of CuO2 - planes per unit cell (n = 1,2,3) and the effect of
La-substitution for Sr for the n = 1 and n = 2 phase were studied
systematically. Furthermore the symmetry of the states could be probed by the
polarization of the impinging radiation.Comment: 4 pages, 2 figures, to appear in the proceedings of SCES2001, Ann
Arbor, August 6-10, 200
Novel Fine-Structure in the Low-Energy Excitation Spectrum of a High-Tc Superconductor by Polarization Dependent Photoemission
Angle-resolved photoemission spectroscopy is performed on single crystals of
the single-layer high-Tc superconductor Bi(2)Sr(2-x)La(x)CuO(6+d) at optimal
doping (x=0.4) in order to study in great detail the Zhang-Rice (ZR) singlet
band at the Fermi level. Besides the high crystal quality the advantages of a
single-layer material are the absence of bilayer effects and the distinct
reduction of thermal broadening. Due to the high energy and angle resolution
and, most important, due to the controlled variation of the polarization vector
of the synchrotron radiation the emission from the ZR singlet band reveals a
distinct fine-structure. It consists of two maxima, the first showing only weak
and the second at EF extremely strong polarization dependence. However, our
observation has enormous consequences for line shape analyses and the
determination of pseudo gaps by photoemission.Comment: 10 pages, 2 figures. to appear in PRB (Rapid Comm.