Nicholas P. Butch, Michael E. Manley, Jason R. Jeffries, Marc Janoschek, Kevin Huang, M. Brian Maple, Jeffrey W. Lynn
Among unconventional electronic ordered states in strongly-correlated materials, one of the most enduring mysteries is the nature of the Hidden Order (HO) phase in URu2Si2 that is characterized by a large entropy change at the ordering temperature of 17.5 K, but that lacks any change in lattice symmetry or magnetic order. Here, we report the temperature dependence of the lattice dynamics of URu2Si2, and find evidence for strong electron-phonon coupling with a conspicuous directional dependence. The phonons are not directly related to the gapped magnetic excitations along the [100] and [001] directions typically associated with the HO phase transition, but instead they exhibit dramatic temperature dependence and softening in the [110] direction. This in-plane anisotropy arises from exceptional electronic structure anomalies and reflects an underlying electron nematic order.
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http://arxiv.org/abs/1212.6238
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