Low-temperature resonant Raman asymmetry in 2H-MoS2 under high pressure
Tsachi Livneh1, Juan S Reparaz2, Alejandro R Goñi2,3
1Department of Physics, Nuclear Research Center, Negev, PO Box 9001, Beer-Sheva, 84190, Israel.
Abstract:
We report on the combined effect of temperature (6 K-300 K) and high pressure (up to 6 GPa) on the resonant Raman scattering by A1g phonons in bulk 2H-MoS2, as the energy of the A exciton is tuned into resonance with an exciting laser at EL = 1.96 eV. As expected, the pressure to be applied for attaining resonant conditions decreases with decreasing temperature. A striking result concerns the combined effect of temperature and pressure on the strength of the incoming relative to the outgoing resonance of the A1g phonon. When its Raman intensity is normalized by that of the 'non-resonant' [Formula: see text] phonon (IA1g/I[Formula: see text]), we find that the contribution of the pressure-tuned outgoing resonance relative to that of the incoming channel changes with temperature. At room temperature both contributions are about equal, as expected. Interestingly, with decreasing temperature an asymmetry in the relative magnitude of the resonances develops, becoming the outgoing contribution about half of the incoming resonance below ~50 K. We discuss the different possibilities for the origin of this effect.
Related Concept Videos
Raman Spectroscopy: Overview
However, a small fraction of the scattered light exhibits a frequency shift due to the exchange of energy between the incident photons and...
IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations
Raman Spectroscopy Instrumentation: Overview
The monochromatic laser source, typically using visible or near-infrared radiation, generates a highly focused beam of light. This light interacts with the molecules of the sample, scattering some of the light. Liquid and gaseous samples are usually tested in ordinary glass capillaries, while solids can be analyzed as powders packed in capillaries or as potassium...
IR Spectroscopy: Hooke's Law Approximation of Molecular Vibration
According to Hooke's law, the vibrational frequency is directly proportional to...
¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution


