The hidden order that develops below 17.5K in the heavy fermion compound URu2Si2 has eluded identification for twenty five years. We show that the recent observation of Ising quasiparticles in URu2Si2 suggests a novel two-component order describing hybridization between electrons and the Ising 5f^{2} states of the uranium atoms. This ``hastatic order'' (Latin: Spear) is distinct from conventional magnetism, because the state that is formed breaks both single and double time-reversal symmetry operations. In so doing, it mixes states of different Kramers parity allowing the conduction electrons to pick up the Ising anisotropy of a spin-1 ion.
We'll talk about bigger the implications of this kind of order, and its predictions for URu2Si2.
* Work carried out in collaboration with Rebecca Flint, MIT and Premi Chandra, Rutgers. arXiv:1207.4828 Supported by NSF DMR 0907179.
