Coupled Ultrafast Lattice and Polarization Dynamics in Ferroelectric Nanolayers

Abstract

We report the first analysis of the polarization and lattice dynamics in a metal/ferroelectric/metal nanolayer system by femtosecond x-ray diffraction. Two Bragg reflections provide information on the coupled dynamics of the two relevant phonon modes for ferroelectricity in perovskites, the tetragonal distortion and the soft mode. Optical excitation of the SrRuO(3) metal layers generates giant stress (>1 GPa) compressing the PbZr(0.2)Ti(0.8)O(3) layers by up to 2%. The resulting change of tetragonality reaches a maximum after 1.3 ps. As a result, the ferroelectric polarization P is reduced by up to 100% with a slight delay that is due to the anharmonic coupling of the two modes.

Ultrafast structural dynamics of perovskite superlattices

“…As discussed in Ref. [25], the (0 0 56) peak is located at a Bragg angle where the slope of the PZT and SRO envelope functions is substantial, making the intensity of this peak most sensitive to angular shifts of the envelopes by transient changes of the individual layer thicknesses. In this way, motions along the coordinate η become visible directly.…”

“…2(a)) [25]. The SL was grown on a STO substrate and consists of a 60 nm thick SRO bottom layer followed by 15 pairs of PZT (Fig.…”

Dynamical coupling inPb(Zr,Ti)O3solid solutions from first principles

“…Ferroelectric (FE) and related materials are of great importance for many device applications 1 . For some of these applications and for fundamental reasons, the dynamical properties of these materials need to be determined and understood, especially when realizing that surprises can be in store when they are investigated [2][3][4][5][6][7][8][9] . For instance, some recent studies discovered that BaTiO 3 has two (rather than one, as believed for more than 30 years) modes contributing to its dielectric response in the THz range, both in the paraelectric and FE tetragonal phases 2,3 .…”

udkm1Dsim—A simulation toolkit for 1D ultrafast dynamics in condensed matter

“…The knowledge of the time-resolved structural response to an ultrafast optical stimulus is essential for the understanding of various condensed matter phenomena. [1][2][3][4] The udkm1Dsim toolbox is a collection of classes and routines to model 1D crystalline sample structures on the atomic level and to simulate incoherent (heat diffusion) as well as coherent lattice dynamics (acoustic phonons) by semi-coupled equations of thermoelasticity. [5,6] The resulting transient X-ray diffraction response for the 1D sample structure is computed by dynamical X-ray theory.…”