Unusual Magnetic Field-Dependence of the Electronic Dispersion Relations in a Hidden Ordered Phase.

Abstract

The Hund's rule exchange interaction promotes a second-order phase transition to a coupled spin and orbital density wave state in the underscreened Anderson Lattice Model. The spin-flip part of the Hund's rule coupling stabilizes a spontaneous spin-dependent mixing of 5f quasiparticle bands that, in the normal state, have pure orbital characters. The transition breaks the spin-rotational invariance and leads to an asymmetric pseudo-gap which forms in the density of states. When a magnetic field is applied, the electronic dispersion relations become dependent on the relative orientation of the field and the spontaneously-chosen quantization axis. We argue that this may result in the magnetic susceptibility of the low-temperature phase becoming anisotropic, but without the development of a static magnetization.

A minimal model for “Hidden Order” in URu2Si2

“…This result is consistent with a recent argument [24]. This finite result for χ ⊥ has a simple interpretation in terms of a Van-Vleck susceptibility.…”

“…In this limit, we find a Hidden Ordered state by using a variational method. Furthermore, the breaking of spin-rotational invariance is connected with the formation of the anisotropy in the magnetic susceptibility [24].…”