Giant magneto-optical Raman effect in a layered transition metal compound

Abstract

We report a dramatic change in the intensity of a Raman mode with applied magnetic field, displaying a gigantic magnetooptical effect. Using the nonmagnetic layered material MoS 2 as a prototype system, we demonstrate that the application of a magnetic field perpendicular to the layers produces a dramatic change in intensity for the out-of-plane vibrations of S atoms, but no change for the in-plane breathing mode. The distinct intensity variation between these two modes results from the effect of field-induced broken symmetry on Raman scattering cross-section. A quantitative analysis on the field-dependent integrated Raman intensity provides a unique method to precisely determine optical mobility. Our analysis is symmetry-based and material-independent, and thus the observations should be general and inspire a new branch of inelastic light scattering and magneto-optical applications.Raman | layered | magneto-optical | broken symmetry | phonon

Magnetic-Field-Induced Quantum Phase Transitions in a van der Waals Magnet

“…In order to probe both the magnetic and crystallographic degrees of freedom in CrI 3 , we carry out polarized Raman spectroscopy to detect the symmetry-resolved collective excitations of spin precessions (i.e., magnons) [17] and lattice vibrations (i.e., phonons) [18][19][20][21], respectively. To further reveal the interplay between these 2 degrees of freedom, we perform both temperature-and magnetic fielddependent Raman measurements covering a temperature (T) range from room temperature down to 10 K and a magnetic field (B) range from 0 up to 7 T. Because the stray magnetic fields cause the Faraday rotation of linearly polarized light transmitted through the objective in close proximity to the magnet [22], we choose circularly polarized light to perform reliable selection rule measurements (see the Supplemental Material Sec. 1 [23] for Raman selection rules in the circular polarization basis for CrI 3 , and see Methods for details of the Raman measurements).…”

Tailoring phonon modes of few-layered MoS2 by in-plane electric field

“…3d), implying a large electro-optical coupling. This gradual increase can be attributed to the manipulation of the MoS 2 electrons under the electric field as it in turn affects the Raman phonon intensity 37 . A more careful look at the Raman spectra reveals the presence of an asymmetry near 377 cm −1 48,49 , which appears due to the transverse optical phonon mode of MoS 2 .…”

“…It has also been used for identification of a number of layers [33][34][35] , and the twist angle between the layers in 2DMs 36 . MoS 2 shows two distinct and well-defined types of Raman modes, one due to the stretching of S atoms along the c axis (A mode) and the other is from the in-plane breathing motion (E 1 2g mode) 12,20,33,37 . The resonance excitation (~1.8-2.0 eV) gives rise to a rich spectrum of second-order peaks and multiphonon bands 26,33 due to strong electron-phonon coupling, and is widely used as the fingerprint characterization of MoS 2 33 .…”

Robust spin-valley polarization in commensurate MoS2 /graphene heterostructures

“…32 is at 4.66 T (Fig. 2(b) inset) in the commensurate MoS 2 /graphene heterostructures, less than the value (~ 6 T) in mechanically exfoliated MoS 2[32], reflecting that the commensurate MoS 2 /graphene heterostructures enjoys higher intrinsic optical mobility and carriers suffer less scattering. This result is in good harmony with the PL spectrum, STEM and STM topographic images of the heterostructures.…”