Ungapped magnetic excitations beyond Hidden Order in URu_2−xRe_xSi₂

ABSTRACT

We use inelastic neutron scattering measurements to show that the energy gap in the magnetic excitations of URu₂Si₂, induced by the Hidden Order transition, is closed by Re substitution. The magnetic excitations remain ungapped in compositions where the specific heat anomaly associated with Hidden Order is no longer observed, which means that the entropy associated with Hidden Order is tied mostly to the magnetic gapping. Further, the onset of ferromagnetic order does not gap the excitations, reflecting the fact that Re substitution does not dramatically affect the Kondo lattice hybridisation.

KEYWORDS:

• Heavy fermion
• hidden order
• spin excitations

Acknowledgments

Access to MACS was provided by the Center for High Resolution Neutron Scattering, a partnership between the National Institute of Standards and Technology and the National Science Foundation under Agreement No. DMR-1508249. Sample synthesis at UCSD was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award No. DE-FG02-04ER46105.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Basic Energy Sciences [grant number DE-FG02-04ER46105]; National Science Foundation [grant number DMR-1508249].