Following
the discovery of superconductivity at 1.5 K, the exact nature of the
pairing mechanism in Sr2RuO4
has attracted a great deal of interest [1]. The main reason is that
superconductivity appears to be highly unconventional, with spin-triplet
pairing and possibly a p-wave order parameter, as opposed to the singlet
d-wave pairing seen in the cuprate high-Tc. Although it is now widely
accepted that superconductivity in Sr2RuO4
is mediated by spin fluctuations, their exact nature is still unresolved
(i.e., either antiferromagnetic or ferromagnetic). Intriguing is also
the variety of different magnetic properties that can be found across
the Ca2-xSrxRuO4
phase diagram, which could hint at the nature of the superconducting
paring mechanism itself [2].
In this regard, important insights could come from the study of the
doping evolution of electronic and magnetic correlations in Ca2-xSrxRuO4
by (spin-resolved) ARPES. This would be the natural continuation of
our detailed investigation (Fig.1)
of the electronic structure of
Sr2RuO4
[3], which allowed us to quantify the effect of
the electronic and/or magnetic correlations, and test the intriguing
hypothesis of a coexistence of superconductivity and
surface
ferromagnetism [4].
Furthermore, low-temperature X-ray absorption experiments on Sr2RuO4
in the superconducting state (i.e., at temperature as low as 200 mK)
have already been planned on the
BACH
beamline at the synchrotron in Trieste (
Elettra).
This study, in which core electrons are excited into the unoccupied
valence band states, could provide us with crucial insights on the change
of symmetry of the electronic wave functions across the superconducting
phase transition.