Sum-frequency ionic Raman scattering

TL;DR

This paper introduces sum-frequency ionic Raman scattering as a new mechanism for exciting Raman-active phonons, expanding the methods for controlling material properties through lattice vibration excitation.

Contribution

It proposes the theoretical concept of sum-frequency ionic Raman scattering and compares it with other Raman mechanisms using density functional theory calculations.

Findings

Sum-frequency ionic Raman scattering is theoretically feasible.

Comparison of four Raman mechanisms across three materials.

Provides a new approach for selective lattice vibration excitation.

Abstract

In a recent report sum-frequency excitation of a Raman-active phonon was experimentally demonstrated for the first time. This mechanism is the sibling of impulsive stimulated Raman scattering, in which difference-frequency components of a light field excite a Raman-active mode. Here we propose that ionic Raman scattering analogously has a sum-frequency counterpart. We compare the four Raman mechanisms, photonic and ionic difference- and sum-frequency excitation, for three different example materials using a generalized oscillator model for which we calculate the parameters with density functional theory. Sum-frequency ionic Raman scattering completes the toolkit for controlling materials properties by means of selective excitation of lattice vibrations.