Resonant optical control of the structural distortions that drive ultrafast demagnetization in Cr${}_2$O${}_3$

Abstract

We study how the color and polarization of ultrashort pulses of visible light can be used to control the demagnetization processes of the antiferromagnetic insulator Cr${}_2$O${}_3$. We utilize time-resolved second harmonic generation (SHG) to probe how changes in the magnetic and structural state evolve in time. We show that, varying the pump photon-energy to excite either localized transitions within the Cr or charge transfer states, leads to markedly different dynamics. Through a full polarization analysis of the SHG signal, symmetry considerations and density functional theory calculations, we show that, in the non-equilibrium state, SHG is sensitive to {\em both} lattice displacements and changes to the magnetic order, which allows us to conclude that different excited states couple to phonon modes of different symmetries. Furthermore, the spin-scattering rate depends on the induced distortion, enabling us to control the timescale for the demagnetization process. Our results suggest that selective photoexcitation of antiferromagnetic insulators allows fast and efficient manipulation of their magnetic state.

arXiv comment7 pages, 5 figures

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Cited by in corpus (7)

• Nonthermal pathways to ultrafast control in quantum materials
• Tracking the ultrafast motion of an antiferromagnetic order parameter
• The magnetic ground state of Sr2IrO4 and implications for second-harmonic generation
• Non-thermal breaking of magnetic order via photo-generated spin defects
• Model of ultrafast demagnetization driven by spin-orbit coupling in a photoexcited antiferromagnetic insulator Cr2O3
• A versatile setup for symmetry-resolved ultrafast dynamics of quantum materials
• Sub-unit cell engineering of CrVO${}_3$ superlattice thin films