Seminar "Direct observation of spin-quadrupolar excitations in Sr2CoGe2O7 by high field ESR" by Mitsuru Akaki

• Date/Time: June 22 (TODAY), 15:00-16:00
• Venue: C015, Lab1
• Speaker: Mitsuru Akaki, Center for Advanced High Magnetic Field Science, Graduate School of Science, Osaka University
• Title: Direct observation of spin-quadrupolar excitations in Sr2CoGe2O7 by high field ESR

Abstract:

Exotic spin-multipolar ordering in large spin transition metal insulators has so far eluded unambiguous experimental observation. A less studied, but perhaps more feasible fingerprint of multipole character emerges in the excitation spectrum in the form of quadrupolar transitions. Such multipolar excitations are desirable as they can be manipulated with the use of light or electric field and can be captured by means of conventional experimental techniques. I will present our study on single crystals of multiferroic Sr2CoGe2O7, and argue that due to its nearly isotropic nature a purely quadrupolar bimagnon mode appears in the electron spin resonance (ESR) spectra. This non-magnetic spin-excitation couples to the electric field of the light and becomes observable for a specific experimental configuration, in full agreement with a theoretical analysis of the selection rules.

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