18 research outputs found
Resonant magnetic exciton mode in the heavy-fermion antiferromagnet CeB6
Resonant magnetic excitations are widely recognized as hallmarks of
unconventional superconductivity in copper oxides, iron pnictides, and
heavy-fermion compounds. Numerous model calculations have related these modes
to the microscopic properties of the pair wave function, but the mechanisms
underlying their formation are still debated. Here we report the discovery of a
similar resonant mode in the non-superconducting, antiferromagnetically ordered
heavy-fermion metal CeB6. Unlike conventional magnons, the mode is
non-dispersive, and its intensity is sharply concentrated around a wave vector
separate from those characterizing the antiferromagnetic order. The magnetic
intensity distribution rather suggests that the mode is associated with a
coexisting order parameter of the unusual antiferro-quadrupolar phase of CeB6,
which has long remained "hidden" to the neutron-scattering probes. The mode
energy increases continuously below the onset temperature for
antiferromagnetism, in parallel to the opening of a nearly isotropic spin gap
throughout the Brillouin zone. These attributes bear strong similarity to those
of the resonant modes observed in unconventional superconductors below their
critical temperatures. This unexpected commonality between the two disparate
ground states indicates the dominance of itinerant spin dynamics in the ordered
low-temperature phases of CeB6 and throws new light on the interplay between
antiferromagnetism, superconductivity, and "hidden" order parameters in
correlated-electron materials