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Phase coexistence and electric-field control of toroidal order in oxide superlattices

Abstract: Systems that exhibit phase competition, order parameter coexistence, and emergent order parameter topologies constitute a major part of modern condensed-matter physics. Here, by applying a range of characterization techniques, and simulations, we observe that in PbTiO"3/SrTiO"3 superlattices all of these effects can be found. By exploring superlattice period-, temperature- and field-dependent evolution of these structures, we observe several new features. First, it is possible to engineer phase coexistence mediated by a first-order phase transition between an emergent, low-temperature vortex phase with electric toroidal order and a high-temperature ferroelectric a"1/a"2 phase. At room temperature, the coexisting vortex and ferroelectric phases form a mesoscale, fibre-textured hierarchical superstructure. The vortex phase possesses an axial polarization, set by the net polarization of the surrounding ferroelectric domains, such that it possesses a multi-order-parameter state and belongs to a class of gyrotropic electrotoroidal compounds. Finally, application of electric fields to this mixed-phase system permits interconversion between the vortex and the ferroelectric phases concomitant with order-of-magnitude changes in piezoelectric and nonlinear optical responses. Our findings suggest new cross-coupled functionalities. © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.

 Fuente: Nature Materials, 2017, 16(10), 1003-1009

 Publisher: Nature Publishing Group

 Publication date: 01/08/2017

 No. of pages: 9

 Publication type: Article

 DOI: 10.1038/NMAT4951

 ISSN: 1476-1122,1476-4660

 Spanish project: FIS2015-64886-C5-2-P

 Publication Url: https://doi.org/10.1038/NMAT4951

Authorship

DAMODARAN, A, R.

CLARKSON, J. D.

HONG, Z.

LIU, H.

YADAV, A. K.

NELSON, Z. T.

SHU, S. L.

MCCARTER, M. R.

PARK, K. D.

KRAVTSOV, V.

FARHAN, A.

DONG. Y.

CAI, Z.

ZHOU, H.

SCHOLL, A.

RASCHKE, M. B.