Proposal for ultrafast switching of ferroelectrics using mid-infrared pulses

TL;DR

This paper proposes a method for ultrafast ferroelectric switching by exciting specific phonon modes with mid-infrared pulses, leading to a nonlinear coupling that enables rapid polarization reversal.

Contribution

It introduces a novel approach using mid-infrared pulses to achieve ultrafast ferroelectric switching via nonlinear phonon mode coupling.

Findings

Large nonlinear coupling between phonon modes in transition-metal oxides.

Discontinuous polarization switching with increasing pump amplitude.

First principles calculations confirm the feasibility of the method.

Abstract

I propose a method for ultrafast switching of ferroelectric polarization using mid-infrared pulses. This involves selectively exciting the highest frequency $A_1$ phonon mode of a ferroelectric material with an intense mid-infrared pulse. Large amplitude oscillations of this mode provides a unidirectional force to the lattice such that it displaces along the lowest frequency $A_1$ phonon mode coordinate because of a nonlinear coupling of the type $g Q_{\textrm{P}} Q_{\textrm{IR}}^2$ between the two modes. First principles calculations show that this coupling is large in transition-metal oxide ferroelectrics, and the sign of the coupling is such that the lattice displaces in the switching direction. Furthermore, I find that the lowest frequency $A_1$ mode has a large $Q_{\textrm{P}}^3$ order anharmonicity, which causes a discontinuous switch of electric polarization as the pump amplitude is continuously increased.