Role of commensurate and incommensurate low-energy excitations in the paramagnetic to hidden-order transition of URu2Si2

P. G. Niklowitz, Sarah Dunsiger, C. Pfleiderer, P. Link, Astrid Schneidewind, Enrico Faulhaber, M. Vojta, Y. -K. Huang, J. A. Mydosh

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We report low-energy inelastic neutron scattering data of the paramagnetic (PM) to hidden-order (HO) phase transition at $T_0=17.5\,{\rm K}$ in URu$_2$Si$_2$. While confirming previous results for the HO and PM phases, our data reveal a pronounced wavevector dependence of quasielastic scattering {\em across} the phase transition. Temperature scans at a small energy transfer of $0.5$~meV establish an abrupt step-like suppression of the excitations at $\vec{Q}_1=\qone$ below $T_0$, whereas excitations at $\vec{Q}_0=\qzero$, associated with large-moment antiferromagnetism (LMAF) under pressure, are enhanced with a pronounced peak {\em at} $T_0$. This is the behavior expected of a ``super-vector'' order parameter with nearly degenerate components for the HO and LMAF leading to nearly isotropic fluctuations in the combined order-parameter space.
Original languageEnglish
Article number115116
Pages (from-to)1-6
Number of pages6
JournalPhysical Review B
Issue number11
Publication statusPublished - 8 Sept 2015

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