795 research outputs found
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
Natural linewidth analysis of d-band photoemission from Ag(110)
We report a high-resolution angle-resolved study of photoemission linewidths
observed for Ag(110). A careful data analysis yields kdd\tau_h \geq 22
d$-hole dynamics in Cu (I.\
Campillo et al., Phys. Rev. Lett., in press) we interpret the lifetime
enhancement by a small scattering cross-section of - and -states below
the Fermi level. With increasing distance to the -hole lifetimes get
shorter because of the rapidly increasing density of d-states and contributions
of intra--band scattering processes, but remain clearly above
free-electron-model predictions.Comment: 14 pages, 7 figure
Comparative study of the electronic structures of the In and Sn/In2O3 (111) interfaces
The electronic structure of the transparent semiconductor In2O3 has been
studied by angle resolved photoemission spectroscopy upon deposition of
metallic indium and also tin on the surface of the semiconductor. By deposition
of metallic indium on In2O3 (111) single crystals, we detected the formation of
a free-electron like band of effective mass (0.38+-0.05) m0. At low coverages,
metallic In shifts the Fermi level of In2O3 to higher energies and a new
electronic state forms at the metal/semiconductor interface. This state of
two-dimensional character (2D-electron gas) is completely responsible for the
electrical conduction in In2O3 (111) at the surface region and has a band
dispersion, which does not correspond to the previously found surface
accumulation layers in this material. Despite the similarity of the electronic
properties of In and Sn, a larger downward banding was observed by Sn coverage,
which was not accompanied by the appearance of the surface state.Comment: 5 pages, 3 figure
Unusual electronic ground state of a prototype cuprate: band splitting of single CuO_2-plane Bi_2 Sr_(2-x) La_x CuO_(6+delta)
By in-situ change of polarization a small splitting of the Zhang-Rice singlet
state band near the Fermi level has been resolved for optimum doped (x=0.4)
BiSrLaCuO at the (pi,0)-point (R.Manzke et al.
PRB 63, R100504 (2001). Here we treat the momentum dependence and lineshape of
the split band by photoemission in the EDC-mode with very high angular and
energy resolution. The splitting into two destinct emissions could also be
observed over a large portion of the major symmetry line M, giving the
dispersion for the individual contributions. Since bi-layer effects can not be
present in this single-layer material the results have to be discussed in the
context of one-particle removal spectral functions derived from current
theoretical models. The most prominent are microscopic phase separation
including striped phase formation, coexisting antiferromagnetic and
incommensurate charge-density-wave critical fluctuations coupled to electrons
(hot spots) or even spin charge separation within the Luttinger liquid picture,
all leading to non-Fermi liquid like behavior in the normal state and having
severe consequences on the way the superconducting state forms. Especially the
possibilty of observing spinon and holon excitations is discussed.Comment: 5 pages, 4 figure
Quasiparticles and Energy Scaling in BiSrCaCuO (=1-3): Angle-Resolved Photoemission Spectroscopy
Angle-resolved photoemission spectroscopy (ARPES) has been performed on the
single- to triple-layered Bi-family high-{\it T} superconductors
(BiSrCaCuO, =1-3). We found a sharp
quasiparticle peak as well as a pseudogap at the Fermi level in the
triple-layered compound. Comparison among three compounds has revealed a
universal rule that the characteristic energies of superconducting and
pseudogap behaviors are scaled with the maximum {\it T}.Comment: 4 pages, 4 figure
Structural behavior of PbBiSrLaCuO for 0<y<0.53
In the Bi cuprates, the presence of a near 15 superstructure is well
known. Usually, this superstructure is suppressed by the substitution of lead,
but there have been reports of a phase separation in so called {\alpha} and
{\beta} phases. This paper shows in high detail time how and why the phase
separation develops and what happens to the quasi-15 superstructure
upon lead substitution. For this purpose, the lanthanum- and lead-substituted
single-layered superconductor BiSrCuO has been
investigated by scanning tunneling microscopy and low-energy electron
diffraction. The La content was kept constant at slightly under-doped
concentration while the Pb content was changed systematically. Thermodynamic
considerations show that a phase mixture of {\alpha} and {\beta} phases is
inevitable.Comment: 17 pages, 4 figure
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