APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013;
Baltimore, Maryland
Session U1: Invited Session: Hidden Order in URu2Si2 and Possibly Related Compounds
11:15 AM–2:15 PM,
Thursday, March 21, 2013
Room: Ballroom I
Sponsoring
Units:
DCMP DCP
Chair: John Mydosh, Kamerlingh Onnes Lab
Abstract ID: BAPS.2013.MAR.U1.4
Abstract: U1.00004 : A Hund's rule mechanism for Hidden Spin-Orbital Density Wave in URu$_2$Si$_2$*
1:03 PM–1:39 PM
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Abstract
Author:
Peter Riseborough
(Temple University)
It is proposed that the ``Hidden Order'' state of URu$_2$Si$_2$ corresponds to a combined spin-orbital density wave state, which is stabilized by the inter-orbital Hund's rule coupling. The electronic system is described by the underscreened Anderson Lattice Model, in which there are two-fold degenerate f bands which hybridize with a single conduction band. In the normal state, the bands at the Fermi-energy have almost pure 5f orbital characters in accord with the results of first principles electronic structure calculations. The model Fermi-surface has heavy fermion sheets which exhibit interband nesting and intraband nesting with similar wave vectors. The spin-flip terms of the Hund's rule interaction and the interband nesting produces a second-order phase transition which partially gaps the Fermi-surface, and leads to a state with broken spin-rotational invariance without forming a net ordered magnetic moment. The resulting spin nematic phase is consistent with the magnetic torque experiments of Okazaki {\it et al.}. The similarity of the interband nesting and the intraband nesting conditions leads to an adiabatic continuity between the ``Hidden Order'' and Antiferromagnetic phases for small values of the hybridization. The presence of a nearby hybridization gap results in an asymmetric form of the pseudogap caused by the ``Hidden Order'' transition. Precursor fluctuations of the hidden order parameter, above $T_{HO}$, lead to the formation of ``hot spots'' on the Fermi-surface and a depletion of the density of states in the vicinity of the Fermi-energy as is seen by point contact and optical spectroscopies. The amplitude of the precursor fluctuations increase as $T_{HO}$ is driven towards zero, however, the order of the transition switches from second-order to first-order pre-empting the quantum critical point. These results in accord with the change in the order of the transition inferred by Jaime {\it et al.} from measurements of the specific heat in an applied magnetic field. This model might also be applicable to the enigmatic pseudo-gap phases seen in high-temperature superconductors.
*This work was supported by the US Department of Energy, Office of Basic Energy Science, Materials Science through grant DEFG02-ER45872.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2013.MAR.U1.4