Coulomb-Enhanced Spin-Orbit Splitting The Missing Piece in the Sr2RhO4 Puzzle.pdf
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Coulomb-Enhanced Spin-Orbit Splitting: The Missing Piece in the Sr2RhO4 Puzzle
Guo-Qiang Liu, V. N. Antonov, O. Jepsen, and O.K. Andersen.
Max-Planck Institut fu?r Festko?rperforschung, D-70569 Stuttgart, Germany
(Dated: July 18, 2008)
The outstanding discrepancy between the measured and calculated (local-density approximation)
Fermi surfaces in the well-characterized, paramagnetic Fermi liquid Sr2RhO4 is resolved by including
the spin-orbit coupling and Coulomb repulsion. This results in an effective spin-orbit coupling
constant enhanced 2.15 times over the bare value. A simple formalism allows discussion of other
systems. For Sr2RhO4, the experimental specific-heat and mass enhancements are found to be 2.2.
PACS numbers: 71.18.+y, 71.20.-b, 71.30.+h
Since the discoveries of high-temperature supercon-
ductivity and colossal magnetoresistance in Mott insula-
tors made metallic by hole-doping, transition-metal ox-
ides have remained at the forefront of research. Their
many lattice and electronic (orbital, charge, and spin)
degrees of freedom are coupled by effective interactions
(electron-phonon, hopping, t, Coulomb repulsion, U, and
Hunds-rule coupling, J), and when some of these are of
similar magnitude, competing phases may exist in the
region of controllable compositions, fields, and tempera-
tures. The interactions tend to remove low-energy de-
grees of freedom, e.g. to reduce the metallicity. This
rarely happens by merely shifting spectral weight from
a quasiparticle band into incoherent Hubbard bands,
as in the U/t-driven metal-insulator transition for the
single-band Hubbard model, but is usually assisted by
lattice distortions which break the degeneracy of low-
energy orbitals and split the corresponding quasiparti-
cle –or partly incoherent– bands away from the chem-
ical potential. According to recent calculations using
the local density-functional plus dynamical me
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