Detall

Conferenciant: Guillaume Nataf (Universitat de Tours).

Resum: Ferroelectric and ferroelastic domain walls are two-dimensional topological defects with thicknesses approaching the unit cell level that can move in response to an electric-field or an applied stress. They exhibit emergent functional properties, such as polarity in non-polar systems or electrical conductivity in otherwise insulating materials, and due their complex strain profiles they interact with phonons as ‘defects’ would [1].

In this talk the lecturer will:

(1) Explain how to image domain walls with optical techniques (polarized light optical microscopy, liquid crystal decoration, Raman spectroscopy (2);

(2) Discuss how they move in response to an electric field, through discrete impulsive jumps, indicators of avalanches on a broad range of scales [3];

(3) Show that they can lead to large thermal conductivity variations in materials.

[1] G.F. Nataf, M. Guennou, J.M. Gregg, D. Meier, J. Hlinka, E.K.H. Salje, J. Kreisel, Domain-wall engineering and topological defects in ferroelectric and ferroelastic materials, Nature Reviews Physics 2, 634–648 (2020).

[2] G.F. Nataf, M. Guennou, Optical studies of ferroelectric and ferroelastic domain walls, J. Phys. Condens. Matter. 32, 183001 (2020).

[3] B. Casals, G.F. Nataf, E.K.H. Salje, Avalanche criticality during ferroelectric/ferroelastic switching, Nature Communications 12, 345 (2021).