Coupled dynamics of long-range and internal spin cluster order in Cu${}_2$OSeO${}_3$

Abstract

Cu${}_4$ triplet clusters form the relevant spin entity for the formation of long-range magnetic order in the cluster magnet Cu${}_2$OSeO${}_3$. Using time-resolved Raman spectroscopy, we probed photoinduced spin and lattice dynamics in this Mott insulator. Multiple ps-decade spin-lattice relaxation dynamics is observed, evidencing a separation of the order parameter dynamics into disordering of long-range and internal spin cluster order. Our study exemplifies the double order parameter dynamics of generalized molecular crystals of charge, spin, and orbital nature.

6 pages, 5 figures