112-2 SEMINAR 柳澤達也(北海道大學物理)-1130327

Time:1130327 (Wed.) 14:20~16:20
Speaker:Prof.柳澤達也(Tatsuya YANAGISAWA) 北海道大學物理學系/Department of Physics, Hokkaido University, Japan
Title:Observation of Multipoles in the Solid State using Ultrasound
Abstract:Ultrasonic measurement is one of the unique and powerful techniques to probe anisotropic local charge distributions and fluctuations in solids [1] associated with the electric/magnetic-multipolar moments of d- or f-orbital, valence/charge fluctuations, atomic vacancy in Si and diamond, and atomic oscillation so called ‘rattling’. These are difficult to be detected by a typical technique such as electrical resistivity and magnetization. In general, the principle of the ultrasonic measurement in solids is based on motoring local strains of the lattice induced by a propagating elastic wave, which is coupled to the local charge distribution and interaction between charge and lattice vibration. As a result, the longitudinal and transverse acoustic waves can observe the multipolar responses of different symmetries “spectroscopically” (Fig. 1). Since the above-mentioned electric degrees of freedom cause a spontaneous symmetry breaking and induce lattice instabilities in some compounds of the strongly correlated electron systems, therefore, it is very important to get the information regarding physical acoustics when exploring a new material. I would like to briefly introduce the recent progress of the ultrasonic studies on strongly correlated electron systems [2-4], and the story of our discovery of elastic softening in the synthetic diamond [5].
[1] B. Lüthi, Physical Acoustics in the Solid State (Springer, Berlin, 2006).
[2] T. Yanagisawa et al., Phys. Rev. Lett. 123, 067201 (2019).
[3] T. Yanagisawa et al., Phys. Rev. Lett. 126, 157201 (2021).
[4] R. Hibino et al., J. Phys. Soc. Jpn. 92, 074708 (2023).
[5] T. Yanagisawa et al., arXiv:2401.03377.
Place:B101, Gongguan Campus, NTNU


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