ELFT HÍRADÓ

[tcsaba <tcsaba AT eik.bme.hu>]

                 M E G H Í V Ó - I N V I T A T I O N

    Seminar Series of the Department of Theoretical Physics at the
           Budapest University of Technology and Economics


                            Karlo Penc
                    (Wigner Research Institute)

       Direct observation of spin-quadrupolar excitations
                 in Sr2CoGe2O7 by high field ESR


Exotic spin-multipolar ordering in 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. Here we study single crystals of 
multiferroic Sr2CoGe2O7 and observe a two-magnon spin excitation 
appearing above the saturation magnetic field in electron spin resonance 
(ESR) spectra. Our analysis of the selection rules reveals that this 
spin excitation mode does not couple to the magnetic component of the 
light, but it is excited by the electric field only, in full agreement 
with the theoretical calculations. Due to the nearly isotropic nature of 
Sr2CoGe2O7, we identify this excitation as a purely spin-quadrupolar 
two-magnon mode.


Időpont: 2018. március 2. péntek, 10:15
Helyszín: BME Fizikai Intézet, Elméleti Fizika Tanszék,
Budafoki út 8. F-épület, III lépcsőház, szemináriumi szoba