Magnetically brightened dark electron-phonon bound states in a van der Waals antiferromagnet

Abstract

In van der Waals (vdW) materials, strong coupling between different degrees of freedom can hybridize elementary excitations into bound states with mixed character. Correctly identifying the nature and composition of these bound states is key to understanding their ground state properties and excitation spectra. Here, we use ultrafast spectroscopy to reveal bound states of d-orbitals and phonons in 2D vdW antiferromagnet NiPS3. These bound states manifest themselves through equally spaced phonon replicas in frequency domain. These states are optically dark above the Néel temperature and become accessible with magnetic order. By launching this phonon and spectrally tracking its amplitude, we establish the electronic origin of bound states as localized d-d excitations. Our data directly yield electron-phonon coupling strength which exceeds the highest known value in 2D systems. These results demonstrate NiPS3 as a platform to study strong interactions between spins, orbitals and lattice, and open pathways to coherent control of 2D magnets.

References in corpus (7)

• Magnetic 2D materials and heterostructures
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• Resolving photon number states in a superconducting circuit
• Suppression of magnetic ordering in XXZ-type antiferromagnetic monolayer NiPS3
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• Universal Substrate Effect on the Superconductivity of FeSe Monolayer Films
• Phonon driven Floquet matter