Exciton-coupled coherent magnons in a 2D semiconductor

Bae, Youn Jue; Wang, Jue; Scheie, Allen; Xu, Jun-Wen; Chica, Daniel G.; Diederich, Geoffrey; Cenker, John; Ziebel, Michael E.; Bai, Yusong; Ren, Haowen; Dean, Cory; Delor, Milan; Xu, Xiaodong; Roy, Xavier; Kent, Andrew D.; Zhu, Xiaoyang

doi:10.1038/s41586-022-05024-1

Cited by 79 publications

(78 citation statements)

References 38 publications

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“…This lack of observable gap evidences highly isotropic magnetism, as one expects for S = 3/2 Cr 3 + . This comports with density functional theory predictions [ 15 ] and recent photon measurements finding Q = 0 magnon gaps of 0.102(3) and 0.141(4) meV, [ 16 ] as well as magnetization measurements finding a maximum anisotropy of 0.144

\rm \mu eV

at 2 K ( c ‐axis compared to b ) in CrSBr (see Supporting Information [ 17 ] ): too small to be resolved in this experiment.…”

Section: Results and Analysissupporting

confidence: 89%

“…This is consistent with the photon excitation study in ref. [16] which finds an interlayer exchange <0.01 meV, as well as density functional calculations in ref. [18] which finds a CrSBr interlayer magnetic interaction three orders of magnitude weaker than the in‐plane interactions.…”

Section: Results and Analysissupporting

confidence: 57%

“…Details of the reaction can be found in ref. [16]. Caution: One end of the tube must be maintained below 120~ °C to prevent the tube from exploding from bromine overpressure.…”

Section: Methodsmentioning

confidence: 99%

“…A modified procedure from ref. [16] was used to synthesize large single crystals of CrSBr. Chromium (0.174 g, 3.35 mmol), sulfur (0.196 g, 6.11 mmol), and CrBr 3 (0.803 g, 2.75 mmol) were loaded into a 12.7 mm O.D., 10.5 mm I.D.…”

Section: Methodsmentioning

confidence: 99%

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Spin Waves and Magnetic Exchange Hamiltonian in CrSBr

et al. 2022

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CrSBr is an air-stable two-dimensional (2D) van der Waals semiconducting magnet with great technological promise, but its atomic-scale magnetic interactions-crucial information for high-frequency switching-are poorly understood. An experimental study is presented to determine the CrSBr magnetic exchange Hamiltonian and bulk magnon spectrum. The A-type antiferromagnetic order using single crystal neutron diffraction is confirmed here. The magnon dispersions are also measured using inelastic neutron scattering and rigorously fit the excitation modes to a spin wave model. The magnon spectrum is well described by an intra-plane ferromagnetic Heisenberg exchange model with seven nearest in-plane exchanges. This fitted exchange Hamiltonian enables theoretical predictions of CrSBr behavior: as one example, the fitted Hamiltonian is used to predict the presence of chiral magnon edge modes with a spin-orbit enhanced CrSBr heterostructure.

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\rm \mu eV

at 2 K ( c ‐axis compared to b ) in CrSBr (see Supporting Information [ 17 ] ): too small to be resolved in this experiment.…”

Section: Results and Analysissupporting

confidence: 89%

Section: Results and Analysissupporting

confidence: 57%

“…Details of the reaction can be found in ref. [16]. Caution: One end of the tube must be maintained below 120~ °C to prevent the tube from exploding from bromine overpressure.…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Spin Waves and Magnetic Exchange Hamiltonian in CrSBr

et al. 2022

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“…The van der Waals (vdW) antiferromagnets, a new class of exfoliatable magnetic materials, provide opportunities for future memory, logic, and communication devices because their magnetic properties are highly tunable, for example, by applied electric fields , or strain, they can possess long-lived magnons, and they can be straightforwardly integrated within complex heterostructures by mechanical assembly. , The strength of exchange coupling between vdW layers is typically much weaker than the direct exchange or superexchange coupling in ordinary three-dimensional crystal antiferromagnets. This weak interlayer exchange yields antiferromagnetic resonances in the gigahertz range, rather than the terahertz range that is more typical for antiferromagnets. − The resonance modes in vdW antiferromagnets can therefore be addressed and controlled with conventional microwave electronics.…”

mentioning

confidence: 99%

Anisotropic Gigahertz Antiferromagnetic Resonances of the Easy-Axis van der Waals Antiferromagnet CrSBr

et al. 2022

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We report measurements of antiferromagnetic resonances in the van der Waals easy-axis antiferromagnet CrSBr. The interlayer exchange field and magnetocrystalline anisotropy fields are comparable to laboratory magnetic fields, allowing a rich variety of gigahertz-frequency dynamical modes to be accessed. By mapping the resonance frequencies as a function of the magnitude and angle of applied magnetic field, we identify the different regimes of antiferromagnetic dynamics. The spectra show good agreement with a Landau−Lifshitz model for two antiferromagnetically coupled sublattices, accounting for interlayer exchange and triaxial magnetic anisotropy. Fits allow us to quantify the parameters governing the magnetic dynamics: At 5 K, the interlayer exchange field is μ 0 H E = 0.395(2) T, and the hard and intermediate-axis anisotropy parameters are μ 0 H c = 1.30(2) T and μ 0 H a = 0.383(7) T. The existence of within-plane anisotropy makes it possible to control the degree of hybridization between the antiferromagnetic resonances using an in-plane magnetic field.

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Probing Defects and Spin‐Phonon Coupling in CrSBr via Resonant Raman Scattering

Torres

Kuc

Maschio

et al. 2023

Adv Funct Materials

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Understanding the stability limitations and defect formation mechanisms in 2D magnets is essential for their utilization in spintronic and memory technologies. Here, defects in mono‐ to multilayer CrSBr are correlated with structural, vibrational, and magnetic properties. Resonant Raman scattering is used to reveal distinct vibrational defect signatures. In pristine CrSBr, it is shown that bromine atoms mediate vibrational interlayer coupling, allowing for distinguishing between surface and bulk defect modes. Environmental exposure is shown to cause drastic degradation in monolayers, with the formation of intralayer defects. This is in contrast to multilayers that predominantly show bromine surface defects. Through deliberate ion irradiation, the formation of defect modes is tuned: these are strongly polarized and resonantly enhanced, reflecting the quasi‐‐1D electronic character of CrSBr. Strikingly, pronounced signatures of spin‐phonon coupling of the intrinsic phonon modes and the ion beam‐induced defect modes are observed throughout the magnetic transition temperature. Overall, defect engineering of magnetic properties is possible, with resonant Raman spectroscopy serving as a direct fingerprint of magnetic phases and defects in CrSBr.

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Exciton-coupled coherent magnons in a 2D semiconductor

Cited by 79 publications

References 38 publications

Spin Waves and Magnetic Exchange Hamiltonian in CrSBr

Spin Waves and Magnetic Exchange Hamiltonian in CrSBr

Anisotropic Gigahertz Antiferromagnetic Resonances of the Easy-Axis van der Waals Antiferromagnet CrSBr

Probing Defects and Spin‐Phonon Coupling in CrSBr via Resonant Raman Scattering

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