Dr. Andreas Bill
ETH Zurich & Paul Scherrer Institute
Title: Influence of
Superconducting Electronic Properties on the Dynamical Magnetic
Susceptibility of High-Tc Materials
Date:
Time: 4:10p.m.
416 Phy/Geo
Angle Resolved
Photoemission Spectroscopy performed on high-temperature superconductors
has established
the increasing importance of long-range pairing interactions with underdoping.
To account for
these experimental findings one has to consider higher harmonics in the
d-wave gap, going
beyond D(k) ~ cos(kx) - cos(ky). It is shown
within a fermiology approach
how the presence
of these higher harmonics affect the incommensurate peaks of the magnetic
susceptibility c(q;w) in the
superconducting state. In particular, it is demonstrated that the contribution
of higher
harmonics renormalizes the spin-gap defined as the smallest energy (at given
wave-vector q)
below which the imaginary part of c(q;w) vanishes.
Furthermore, a crossover
from parallel to
diagonal incommensurate peaks is observed at the resonance energy. Finally, a
relation is established
between the peak structure and the minima of the two-particle excitation
continuum. Recent
inelastic neutron scattering experiments performed on several high-Tc materials
are discussed in
the light of the present results.