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

Journal Article

Damodaran, A.R, J.D Clarkson, Z Hong, H B Liu, A.K Yadav, C.T Nelson, S.-L Hsu, M.R McCarter, K.-D Park, V Kravtsov, A Farhan, Y Dong, Z Cai, H Zhou, P Aguado-Puente, P García-Fernández, J Íñiguez, J Junquera, A Scholl, M.B Raschke, L.-Q Chen, D.D Fong, Ramamoorthy Ramesh, L.W Martin

10.1038/NMAT4951

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.

Nature Materials

16

2017

14761122

cited By 50

Ramesh Lab