Ultrasonic study of the hidden order and heavy-fermion state in URu₂Si₂ with hydrostatic pressure, Rh-doping, and high magnetic fields

Abstract

This paper reports recent progress of ultrasonic measurements on URuSi, including ultrasonic measurements under hydrostatic pressure, in pulsed magnetic fields, and the effect of Rh-substitution. The observed changes of the elastic responses shed light on the orthorhombic-lattice instability with -symmetry existing within the hidden order and the hybridized 5-electron states of URuSi.

Keywords:

• URu₂Si₂
• hidden order
• hybridization
• ultrasound
• elastic constant
• lattice instability
• pulsed magnetic field
• hydrostatic pressure
• band Jahn–Teller effect

Acknowledgements

The author would like to thank H. Saitoh, Y. Watanabe, and S. Mombetsu (Hokkaido Univ.), who contributed to the construction of the ultrasonic apparatus, and K. Hiura and T. Murazumi (Hokkaido Univ.) for helping with ultrasonic measurements. The author also thanks W. Knafo (LNCMI, Toulouse) and H. Kusunose (Ehime Univ.) for fruitful discussions. The ultrasonic measurements and sample growth done at Hokkaido University were performed in collaboration with M. Yokoyama (Ibaraki Univ.), Y. Ikeda (ISSP, Univ. of Tokyo), H. Hidaka, and H. Amitsuka (Hokkaido Univ.). Pulsed magnetic field measurements were performed in collaboration with M. Akatsu (Niigata Univ.), S. Yasin, S. Zherlitsyn, and J. Wosnitza (Helmholtz-Zentrum Dresden-Rossendorf). A single crystal used in the pulsed field measurements was grown at Univ. of California San Diego, in cooperation with M.B. Maple, K. Huang (UC San Diego) and M. Janoschek (Los Alamos Natl. Lab.). We also acknowledge the support of the Hochfeld-Magnetlabor Dresden at HZDR, a member of the European Magnetic Field Laboratory.