Unveiling Intervalley Scattering In 2D Crystals

What Has Been Achieved

A family of longstanding mis-assignments of Raman signatures in 2D transition metal dichalcogenides has been corrected by the collaboration between double resonance Raman spectroscopy experiments and first-principles calculations. Selection rules for intervalley scattering processes in MoS2 have been derived from group theory and verified from first-principles.

Importance of Achievement

The study establishes the dominance of LA(K) phonons in intervalley scattering, a process responsible for the destruction of valley polarization, thus highlighting the need for controlling this phonon mode for future efforts on valleytronic devices.

Unique Features of the MIP That Enabled Project

Close collaboration between synthesis, characterization, and theory efforts.


B. R. Carvalho, Y. Wang, S. Mignuzzi, D. Roy, M. Terrones, C. Fantini, V. H. Crespi, L. M. Malard, and M. A. Pimenta, “Intervalley scattering by acoustic phonons in two-dimensional MoS2 revealed by double-resonance Raman spectroscopy”, Nat. Commun. 8, 14670 (2017).


Vibrational Responses in Molybdenum Disulfide. The energies of electrons in monolayer MoS2 is shown to determine the link between two types of interactions: electron with light, and electron with lattice vibrations. For example, the lower panel shows two different vibrational responses when the material is excited with light at different wavelengths.
Carvalho, Wang, Mignuzzi, Roy, Terrones, Fantini, Crespi, Malard, Pimenta, Universidade Federal de Minas Gerais, Penn State, King’s College London
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