Letter abstract
Nature Physics 3, 96 - 99 (2007)
doi:10.1038/nphys522
Subject Categories: Condensed-matter physics | Statistical physics, thermodynamics and nonlinear dynamics | Materials physics
Gapped itinerant spin excitations account for missing entropy in the hidden-order state of URu2Si2
C. R. Wiebe1,2, J. A. Janik1,2, G. J. MacDougall3, G. M. Luke3, J. D. Garrett4, H. D. Zhou2, Y.-J. Jo2, L. Balicas2, Y. Qiu5,6, J. R. D. Copley5, Z. Yamani7 and W. J. L. Buyers7
Many correlated electron materials, such as high-temperature superconductors1, geometrically frustrated oxides2 and low-dimensional magnets3, 4, are still objects of fruitful study because of the unique properties that arise owing to poorly understood many-body effects. Heavy-fermion metals5—materials that have high effective electron masses due to those effects—represent a class of materials with exotic properties, ranging from unusual magnetism, unconventional superconductivity and 'hidden' order parameters6. The heavy-fermion superconductor URu2Si2 has held the attention of physicists for the past two decades owing to the presence of a 'hidden-order' phase below 17.5 K. Neutron scattering measurements indicate that the ordered moment is 0.03
B, much too small to account for the large heat-capacity anomaly at 17.5 K. We present recent neutron scattering experiments that unveil a new piece of this puzzle—the spin-excitation spectrum above 17.5 K exhibits well-correlated, itinerant-like spin excitations up to at least 10 meV, emanating from incommensurate wavevectors. The large entropy change associated with the presence of an energy gap in the excitations explains the reduction in the electronic specific heat through the transition.
- Department of Physics, Florida State University, Tallahassee, Florida 32306-3016, USA
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306-4005, USA
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada
- Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario L854M1, Canada
- NIST Center for Neutron Research, Gaithersburg, Maryland 20899-8562, USA
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA
- CNBC, National Research Council, Chalk River Labs, Chalk River, Ontario K0J 1J0, Canada
Correspondence to: C. R. Wiebe1,2 e-mail: cwiebe@magnet.fsu.edu
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