Photoinduced strain and polarization switching in barium titanate in the far-infrared spectral range

TL;DR

This study explores how far-infrared excitation (5-8 THz) induces transient strain and polarization switching in ferroelectric BaTiO3, revealing absorption-driven effects distinct from mid-infrared mechanisms.

Contribution

It demonstrates polarization switching in BaTiO3 driven by far-infrared excitation, highlighting absorption effects over phonon or epsilon-near-zero influences.

Findings

Polarization switching persists across 5-8 THz range.

Switching is primarily governed by optical absorption.

Mechanisms differ from mid-infrared excitation effects.

Abstract

Short mid-infrared laser pulses efficiently facilitate ultrafast manipulation of ferroic order parameters, including full reversal of magnetization or ferroelectric polarization, with the invoked mechanisms relating to the properties of polar phonons in ionic crystals. Much less is known, however, about the behaviour of such order parameters in response to an excitation in the far-infrared range, where phonons are more collective and less polar. Here we investigate transient crystallographic strains and polarization switching in ferroelectric barium titanate (BaTiO3) driven by an excitation in the frequency range of 5-8 THz, or wavelengths of 35-60 um. We find that switching persists in a large part of this range, but is governed primarily by optical absorption rather than by the longitudinal optical phonons or epsilon-near-zero conditions that dominate in the mid-infrared regime.