Description
I will briefly review the rudiments of orbital order physics
and then discuss several more recent results. Orbitals are
described by SU(2) operators but unlike spins the orbitals
live in real space and thus their interactions are highly
frustrated. It will be shown that spatial orders of
electronic orbital states in a crystal can be triggered by
thermal fluctuations alone (contrary to earlier lore, no
zero point
quantum fluctuations are necessary to stabilize orders). It
will be further shown how symmetry considerations alone give
rise to dimensional reduction as well as topological order
and selection rules that may be experimentally tested from
scattering measurements. I will illustrate that in addition
to charge and spin order driven quantum critical points,
Orbital Order Driven Quantum Criticality, as a matter of
principle, also occur in the simplest orbital Hamiltonians.
New predicted orbital nematic orders will be demonstrated in
some of the best known orbital dependent Hamiltonians.
Primary author
Prof.
Zohar Nussinov
(Washington university)
