Title: Dr. Tatsuya Yanagisawa: A study of elastic properties of URu2Si2 by using ultrasound with pulsed-magnetic fields
Number: 1/15
Status: Closing date exceeded
Begin: Pátek, 20.02. 2015, 14:00
Tutor: Dr. Tatsuya Yanagisawa
Location: lecture room F2, first floor Ke Karlovu 5

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 We have a pleasure to invite you to attend the joint seminar
of the Department of Condensed Matter Physics (DCMP)
and the Magnetism and Low Temperature Laboratories (MLTL),
supported within the program of Czech Research Infrastructures (project no. LM2011025).



A study of elastic properties of URu2Si2 by using ultrasound with pulsed-magnetic fields



lecture given by:

Dr. Tatsuya Yanagisawa

Division of Physics, Faculty of Science, Hokkaido University, Japan


The seminar takes place in the lecture room F2
of the Faculty of Mathematics and Physics, Ke Karlovu 5, Praha 2
on Friday, 20.2.2015 from 14.00 


Vladimír Sechovský
On behalf of the DCMP and MLTL


Heavy-fermion superconductor URu2Si2 has been known to show an enigmatic second-ordered phase transition at 17.5 K, whose order parameter has been unsolved since its discovery over 25 years ago [1–3]. Many research efforts have been made to identify the broken symmetry of the phase transition; however, conclusive results have not been obtained yet.

Ultrasonic measurement is a powerful tool to probe electric multipole responses and symmetry-breaking lattice instabilities in single crystals; using the bulk elastic response of solid states via electron-phonon coupling, by means of sound-velocity measurement, it produces accuracies up to dv/v 1e−7. We have performed precise ultrasonic measurements on single-crystalline URu2Si2 under pulsed-magnetic field up to 68.7 T in wide temperature range from 1.5 K to 116 K to check for possible lattice instabilities of this compound. 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 // c associated with the successive transitions above ~35 T [4]. The present results strongly suggest that the B1g: G3, (x2 - y2)-type, symmetry-breaking orthorhombic lattice instability could result from local-symmetry-breaking band instability via conduction electron to f-electron hybridization and will be linked to the hidden order parameter of this compound.

In Dresden, we are now performing more ultrasonic measurements of URu2Si2 by using different geometries in order to see the elastic response of other transverse modes with different symmetries, such as C44 (Eg: G5) and C66 (B1g: G4). These recent research progress will also be discussed.


[1] M. B. Maple et al.: Phys. Rev. Lett. 56 (1986) 185.
[2] W. Schlabitz et al.: Z. Phys. B 62 (1986) 171.
[3] T. T. M. Palstra et al.: Phys. Rev. Lett. 55 (1985) 2727.
[4] T. Yanagisawa et al.: Phys. Rev. B 88 (2013) 195150; Phil. Mag.  94 (2014) 3775.