We have performed ultrasonic measurements on single-crystalline URu2Si2 with pulsed magnetic fields, in order to check for possible lattice instabilities due to the hybridized state and the hidden-order state of this compound. The elastic constant (C11-C12)/2, which is associated with a response to the {\Gamma}3-type symmetry-breaking (orthorhombic) strain field, shows a three-step increase at H > 35 T for H || c at low temperatures, where successive meta-magnetic transitions are observed in the magnetization. We discovered a new fact that the absolute change of the softening of (C11-C12)/2 in the temperature dependence is quantitatively recovered at the suppression of hybridized-electronic state and the hidden order in high-magnetic field for H \perp c associated with the successive transitions. The present results suggest that the {\Gamma}3-type lattice instability, is related to both the emergence of the hybridized electronic state and the hidden-order parameter of URu2Si2. On the other hand, magnetic fields H || [100] and [110] enhance the softening of (C11-C12)/2 in the hidden order phase, while no step-like anomaly is observed up to 68.7 T. We discuss the limitation of the localized-electron picture for describing these features of URu2Si2 by examination of a crystalline electric field model in terms of mean-field theory.
@article{arxiv.1211.7185,
title = {{\Gamma}3-type Lattice Instability and the Hidden Order of URu2Si2},
author = {Tatsuya Yanagisawa and Shota Mombetsu and Hiroyuki Hidaka and Hiroshi Amitsuka and Mitsuhiro Akatsu and Shadi Yasin and Sergei Zherlitsyn and Jochen Wosnitza and Kevin Huang and M. Brian Maple},
journal= {arXiv preprint arXiv:1211.7185},
year = {2012}
}