The ultrafast response of polar vortices under optical excitation
ORAL
Abstract
Polar vortices were recently discovered in PbTiO$_{\mathrm{3}}$-SrTiO$_{\mathrm{3}}$ superlattices [1], stabilized at the nanoscale in the presence of depolarizing fields and mechanical stresses. We have found that these exotic structures, non-existent in the bulk ferroelectrics, possess rich ultrafast responses to fs laser excitation, which is attractive for high-density information storage and nanoscale actuation. Using optical pulse excitation above the bandgap of PbTiO$_{\mathrm{3}}$ layers and structural and second harmonic generation probes of ferroelectric order dynamics, a series of reversible and irreversible nano-ordering transitions were observed. X-ray diffraction and diffuse scattering on nanodomains aided the phase identification during time-resolved measurements. In this talk, we will discuss the dynamic interplay between collinear and toroidal ferroelectric domains aided by understanding from phase field modelling. [1] A.K. Yadav, R. Ramesh et el., "Observation of Polar Vortices in Oxide Superlattices", accepted, Nature (2015).
*DE-SC0012375, DE-AC02-06CH11357, U.S Department of Energy, Office of Science, Office of Basic Energy Sciences
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