Condensed Matter Seminars

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.