TRR 360 Seminar:

Multi-Extreme THz ESR Study of the Pressure-Induced Phase Transition in the Shastry-Sutherland Model Substance SrCu₂(BO₃)₂

Hitoshi Ohta

Multi-Extreme THz ESR Study of the Pressure-Induced Phase Transition in the Shastry-Sutherland Model Substance SrCu₂(BO₃)₂

Prof. Dr. Hitoshi Ohta

Molecular Photoscience Research Center, Kobe University, Japan
Research Center for Development of Far-Infrared Region, University of Fukui, Japan

We have been developing THz ESR under multi-extreme conditions, such as high magnetic field, high pressure and low temperature in Kobe. It covers the frequency region between 0.03 and 7 THz,¹ the temperature region between 1.8 and 300 K,¹ the magnetic field region up to 55 T,¹ and the pressure region is extended from 1.5 GPa² to 2.5 GPa using the hybrid-type piston-cylinder pressure cell.³ It also includes mechanically detected ESR⁴ measurements using a commercially available membrane-type surface stress sensor, which is the extension from our micro-cantilever ESR⁵. As an example, application of high pressure THz ESR to understand the pressure-induced phase transition in the Shastry-Sutherland model substance SrCu₂(BO₃)₂ will be discussed. Using our technique, we were able to determine the pressure where the pressure-induced phase transition occurs, and obtain the pressure dependence of exchange interactions in SrCu₂(BO₃)₂ [Ref. 6]. Comparison of our results with the theory will be discussed.

1. H. Ohta et al., J. Low Temp. Phys. 2013, 170, 511.
2. T. Sakurai et al., Rev. Sci. Inst. 2007, 78, 065107
3. K. Fujimoto et al., Appl. Mag. Res. 2013, 44, 893; H. Ohta et al., J. Phys. Chem. B 2015, 119, 13755; T. Sakurai et al., J. Mag. Res., 2015, 259,108.
4. H. Takahashi et al., Rev. Sci. Intrum. 2018, 89, 036108
5. H. Ohta et al., AIP Conf. Proceedings 2006, 850, 1643; E. Ohmichi et al., Rev. Sci. Instrum. 2008, 79, 103903; H. Takahashi et al., Appl. Phys. Lett. 2015, 107, 182405.
6. T. Sakurai et al., J. Phys. Soc. Jpn. 87 (2018) 033701