SPring-8, the large synchrotron radiation facility

Speaker: KIDA Noriaki

Language: Japanese

Affiliation: AMS(Advanced Materials Science), Graduate School of Frontier Sciences, The University of Tokyo

Title: New Developments in Solid State Physics Using Terahertz and Mid-Infrared Pulse

Abstract:
　Recent advances in femtosecond laser technology make it possible to generate and detect new electromagnetic waves called terahertz pulses. The terahertz pulse refers to a nearly monocyclic electromagnetic field pulse with a center frequency of about 1 THz, which corresponds to photon energy of about 4 meV, and time width of about 1 ps. Spectroscopic measurements using terahertz pulses have the advantage that changes in the amplitude and phase of the terahertz electric field can be detected simultaneously, making it possible to determine both the real and imaginary parts of the optical constants of solids without approximation. It has been demonstrated that these features of terahertz pulses can be used for imaging polarized (magnetic) domains of ferroelectric (ferromagnetic) materials. On the other hand, the electric field amplitude of terahertz pulses can be enhanced to 1 MV/cm or more. These pulses are used not only as probe light to investigate the optical response of solids but also as excitation light to control electronic and crystal structures of solids. Very recently, generation of phase-locked intense mid-infrared pulses with amplitudes exceeding 10 MV/cm are realized, and research to control the physical properties of solids begins.
　In this seminar, first I introduce our research, focusing on the following three topics.
(1) Detection of electromagnons (magnetic excitations excited by electric fields) in multiferroics by terahertz spectroscopy at low-temperatures and in magnetic fields ^[1,2].
(2) Domain imaging of ferroelectric and ferromagnetic materials using terahertz radiation ^[3-5].
(3) Coherent control of polarization and structure of electron-type dielectrics using intense terahertz and mid-infrared pulses ^[6-9].
In the latter, I discuss the possibilities and prospects of pump-and-probe spectroscopy combining XFEL and terahertz and mid-infrared pulses as future developments in solid state physics.

[1] N. Kida et al., Phys. Rev. B 80, 220406(R) (2009).
[2] N. Kida et al., Phys. Rev. B 83, 064422 (2011).
[3] M. Sotome et al., Appl. Phys. Lett. 105, 041101 (2014).
[4] Y. Kinoshita et al., ACS Photonics 3, 1170 (2016).
[5] Y. Kinoshita et al., Phys. Rev. Lett. 124, 057402 (2020).
[6] T. Morimoto et al., Phys. Rev. Lett. 118, 107602 (2017).
[7] T. Miyamoto et al., Sci. Rep. 8, 15014 (2018).
[8] H. Yamakawa et al., Nat. Commun. 12, 953 (2021).
[9]T. Morimoto et al. Phys. Rev. Research 3, L042028 (2021).