Effects of disorder with finite range on the properties of d-wave superconductors
Simon Scheffler
I. Institut für Theoretische Physik, Universität Hamburg, Jungiusstr. 9, 20355 Hamburg, Germany
It has long been established that disorder has profound effects on
unconventional superconductors and it has been suggested repeatedly that
observation and analysis of these disorder effects can help to identify
the order parameter symmetry. In much of the relevant literature,
including very sophisticated calculations of interference and weak
localization effects, the disorder is represented by delta-function
scatterers of arbitrary strength. One obvious shortcoming of this
approximation is that resonant scattering resulting from the wavelength of
the scattered quasiparticle matching the spatial extent of the defect is
not included. We find that the mitigation of the Tc-reduction, expected
when d-wave scattering is included, is very sensitive to the average
strength of the scattering potential and is most effective for weak
scatterers. Disorder with finite range not only has drastic effects on the
predicted density of states at low energies, relevant for transport
properties, but affects the spectral function at all energies up to the
order parameter amplitude. The gap structure, which does not appear to be
of the simplest d-wave form, should show a defect-dependent variation with
temperature, which could be detected in ARPES experiments.
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