Hidden Order and Low-Energy Excitations in NpO2
Abstract
We investigate the nature of the hidden order parameter in the ordered phase of NpO2, which had been identified with a staggered arrangement of Γ5 magnetic multipoles. By analyzing the existing experimental data, we show that the most likely driving order parameter is not provided by octupoles, as usually assumed, but rather by the rank-5 triakontadipoles. Calculations of the coupled dynamics of spins, Γ5 quadrupoles, and Γ5 triakontadipoles in the ordered phase enable us to analyze the resulting structure of low-energy excitations. We show that the powder inelastic neutron scattering cross section should contain, in addition to the already-observed peak at 6.5 meV, a second weaker peak at about 14 meV.
- Publication:
-
Physical Review Letters
- Pub Date:
- November 2006
- DOI:
- 10.1103/PhysRevLett.97.207203
- Bibcode:
- 2006PhRvL..97t7203S
- Keywords:
-
- 75.10.Dg;
- 75.40.Cx;
- 75.40.Gb;
- Crystal-field theory and spin Hamiltonians;
- Static properties;
- Dynamic properties