Emergent topological polar structures in freestanding complex oxide membranes

Abstract: 

Complex correlated oxides are quantum materials characterized by unshielded d-electrons in which the interaction across competing energy scales leads to diverse functionalities that can be altered by slight changes of their structure, composition, or boundary conditions [1]. In this context, recent studies on ferroelectric oxides have shown the formation of complex polar topologies, which are related to a delicate interplay between the intrinsic tendency of the material towards a uniform polarization and the electrical and mechanical constraints placed upon them [2]. However, the cube-on-cube epitaxial structure of these materials forces the use of single crystalline substrates for their growth, which restricts the possible mechanical boundary conditions and, therefore, the formation of new topological structures.

This seminar will introduce a novel approach to form a non-trivial topological polar state [3]. This is achieved by isolating epitaxially grown ferroelectric thin films from their parent substrate by a chemical exfoliation method and fabricating twisted freestanding ferroelectric bilayers, in which an unconventional strain landscape produces a vortex polarization pattern that is dependent on the twisting angle. This finding opens the path to creating novel topological textures, of just a few nm in size, that could serve as the base of innovative high-density memory devices.

References:
[1] Y. Tokura et al., Nature 13, 1056 (2017)
[2] Yadav, A. K. et al., Nature, 530, 198 (2016).
[3] G. Sánchez-Santolino, V. Rouco et al., Nature, 626, 529 (2024)

Short biography:

Gabriel Sánchez Santolino received his BSc and Ph.D. (2015) in Physics from the Complutense University of Madrid. During his Ph.D., he also carried out part of his research at the STEM group at Oak Ridge National Laboratory. From 2015 to 2017 he joined the Crystal Interface Laboratory at the University of Tokyo and worked on the study of localized electric fields in materials by differential phase contrast in the electron microscope. In 2017, he obtained a Juan de la Cierva postdoctoral fellowship and joined the 2D Foundry group at the Spanish National Research Council in the Institute of Materials Science of Madrid (ICMM-CSIC). In 2019 He joined the Eva Olsson Group at Chalmers University of Technology. From 2020, he is a member of the Group on Physics of Complex Materials at Complutense University of Madrid where he joined as a Jóvenes Investigadores Researcher and then obtained a Ramon y Cajal tenure track position. His main research interest is the study of emergent physical phenomena in complex materials by advanced electron microscopy techniques.

To get an assistance certificate for this seminar, please, register here: https://docs.google.com/forms/d/e/1FAIpQLSeW4w4RwQWVmYuQYnXgTAPp_OhqgDqgI07UMAcFjaH1GVefng/viewform?usp=header