Observation of the polaronic character of excitons in a two-dimensional semiconducting magnet $\mathrm{Cr}{\mathrm{I}}_3$

Abstract

Exciton dynamics can be strongly affected by lattice vibrations through electron-phonon coupling. This is rarely explored in two-dimensional magnetic semiconductors. Focusing on bilayer CrI3, we first show the presence of strong electron-phonon coupling through temperature-dependent photoluminescence and absorption spectroscopy. We then report the observation of periodic broad modes up to the 8th order in Raman spectra, attributed to the polaronic character of excitons. We establish that this polaronic character is dominated by the coupling between the charge-transfer exciton at 1.96 eV and a longitudinal optical phonon at 120.6 cm-1. We further show that the emergence of long-range magnetic order enhances the electron-phonon coupling strength by about 50$\%$ and that the transition from layered antiferromagnetic to ferromagnetic order tunes the spectral intensity of the periodic broad modes, suggesting a strong coupling among the lattice, charge and spin in two-dimensional CrI3. Our study opens opportunities for tailoring light-matter interactions in two-dimensional magnetic semiconductors.

21 pages, 4 figures + Supplementary Information

References in corpus (7)

• Evolution of interlayer and intralayer magnetism in three atomically thin chromium trihalides
• Tuning Inelastic Light Scattering via Symmetry Control in 2D Magnet CrI${}_3$
• Phonon driven Floquet matter
• Distinct magneto-Raman signatures of spin-flip phase transitions in CrI3
• Magnetic field-induced quantum phase transitions in a van der Waals magnet
• Magnetic order induced polarization anomaly of Raman scattering in 2D magnet CrI${}_3$
• Magnetic polaron and antiferro-ferromagnetic transition in doped bilayer CrI${}_3$

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• A Combined First Principles Study of the Structural, Magnetic, and Phonon Properties of Monolayer CrI${}_3$
• Progress and Prospects in Two-Dimensional Magnetism of van der Waals Materials
• Optical and magneto-optical properties of ferromagnetic monolayer CrBr${}_3$: A first-principles $GW$ and $GW$ plus Bethe-Salpeter equation study
• Structural Monoclinicity and Its Coupling to Layered Magnetism in Few-Layer $\mathrm{Cr}{\mathrm{I}}_3$
• Nearly-Resonant Crystalline-Phononic Coupling in Quantum Spin Liquid Candidate CsYbSe${}_2$
• Magnetoelectric effect in van der Waals magnets
• Polaronic and Mott insulating phase of layered magnetic vanadium trihalide VCl3
• Superexchange and spin-orbit coupling in monolayer and bilayer chromium trihalides
• Large cross-polarized Raman signal in CrI${}_3$: A first-principles study
• Brightened Optical Transition as Indicator of Multiferroicity in a Layered Antiferromagnet
• Dispersive dark excitons in van der Waals ferromagnet CrI3
• Group Theory Analysis of Phonons in Monolayer Chromium Trihalides and Their Janus Structures
• Monolayer-to-mesoscale modulation of the optical properties in 2D CrI3 mapped by hyperspectral microscopy
• Orbital mixing and strong Hund's coupling stabilize spin order in van der Waals ferromagnet CrI3
• Activated Migration of Localized Ligand-Field Excitons in Atomically Thin CrCl3