Ultrafast Dynamics of Spin-Orbit Entangled Excitons Coupled to Magnetic Ordering in van der Waals Antiferromagnet NiPS3

Abstract

Spin-orbit entangled excitons (SOEE) in two-dimensional (2D) antiferromagnets provide direct access to explore unconventional many body interactions in correlated electron systems. In this work, we carry out a detailed investigation using non-degenerate isotropic and anisotropic pump-probe reflection spectroscopy to probe the ultrafast dynamics of SOEE and their coupling to spin fluctuations in NiPS3. Transient reflectivity data reveals acoustic phonon oscillations at ~ 27 GHz, along with two distinct relaxation timescales: fast (1-9 ps) and slower components (1-4 ns) associated with SOEE coherence and spin reordering, respectively. Both timescales exhibit pronounced temperature dependence near the exciton dissociation (TED = 120 K) and Neel (TN = 155 K) temperatures. The SOEE coherence shortens from ~ 8-9 ps at T < TED to ~ 3 ps at T > TED with a finite tail persisting beyond TN. The spin reordering time grows near 120 K, and shows critical slowing down around TN. Pump fluence studies further corroborate their spin origin. Our findings uncover the direct interplay between the excitonic and spin degrees of freedom across ultrafast and longer timescales, offering new opportunities to probe and engineer emergent many-body interactions in 2D antiferromagnets.

28 pages, 22 figures

References in corpus (16)

• Suppression of magnetic ordering in XXZ-type antiferromagnetic monolayer NiPS3
• Highly Anisotropic Excitons and Multiple Phonon Bound States in a Van der Waals Antiferromagnetic Insulator
• Exciton-driven antiferromagnetic metal in a correlated van der Waals insulator
• Spin-correlated exciton-polaritons in a van der Waals magnet
• Temperature dependent Raman and x-ray studies of spin-ice pyrochlore $D{y}_{2}T{i}_2{O}_7$ and non-magnetic pyrochlore $L{u}_{2}T{i}_2{O}_7$
• Highly sensitive spin-flop transition in antiferromagnetic van-der Waals material MPS3 (M = Ni and Mn)
• Magnetically brightened dark electron-phonon bound states in a van der Waals antiferromagnet
• Magnetically propagating Hund's exciton in van der Waals antiferromagnet NiPS3
• Spin wave Hamiltonian and anomalous scattering in NiPS${}_3$
• Dynamical criticality of spin-shear coupling in van der Waals antiferromagnets
• Influence of spin and orbital fluctuations on Mott-Hubbard exciton dynamics in LaVO${}_3$ Thin Films
• Low-energy excitations and magnetic anisotropy of the layered van der Waals antiferromagnet Ni${}_2$P${}_2$S${}_6$
• Laser-induced Demagnetization in van der Waals $XY$- and Ising-like Antiferromagnets NiPS${}_3$ and FePS${}_3$
• Distinct Optical Excitation Mechanisms of a Coherent Magnon in a van der Waals Antiferromagnet
• Long-lived population inversion in resonantly driven excitonic antiferromagnet
• Characteristic exciton energy scales in antiferromagnetic NiPS${}_3$