Patrik Fazekas

Group theory and octupolar order in URu 2Si 2

Recent experiments on

Orbital degeneracy as a source of frustration in LiNiO2

\mathrm{U}{\mathrm{Ru}}_{2}{\mathrm{Si}}_{2}

Pressure induced quantum critical point and non-Fermi-liquid behavior in BaVS3

show that the low-pressure hidden order is nonmagnetic but it breaks time reversal invariance. Restricting our attention to local order parameters of

Sequence of multipolar transitions : Scenarios for URu2Si2

5{f}^{2}

Gutzwiller variational theory for the Hubbard model with attractive interaction

shells, we find that the best candidate for hidden order is staggered order of either

Orbital order in degenerate Hubbard models : A variational study

{\mathcal{T}}_{z}^{\ensuremath{\beta}}

Orbital order and spin–orbit coupling in BaVS3

or

Electrical properties of Cd2Re2O7 under pressure

{\mathcal{T}}_{xyz}

Electrical properties ofCd2Re2O7under pressure

octupoles. Group theoretical arguments for the effect of symmetry-lowering perturbations (magnetic field, mechanical stress) predict behavior in good overall agreement with observations. We illustrate our general arguments on the example of a five-state crystal field model which differs in several details from models discussed in the literature. The general appearance of the mean field phase diagram agrees with the experimental results. In particular, we find that (a) at zero magnetic field, there is a first-order phase boundary between octupolar order and large-moment antiferromagnetism with increasing hydrostatic pressure; (b) arbitrarily weak uniaxial pressure induces staggered magnetic moments in the octupolar phase; and (c) a new phase with different symmetry appears at large magnetic fields.

Multichannel Kondo necklace.

Motivated by the absence of cooperative Jahn-Teller effect and of magnetic ordering in LiNiO