Dr. Anna Razumnaya
Jožef Stefan Institute
Jamova cesta 39
Ljubljana, Slovenija
anna.razumnaya@ijs.si
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Anna Razumnaya is a scientific associate at the JSI. She earned a PhD in physics from the University of Picardie, France, and was awarded an MSCA Postdoctoral Fellowship at JSI for the period 2022-2024.
Dr. Anna Razumnaya's current research interest focuses on investigating topological polarization textures and chirality in ferroic nanomaterials, including ferroelectrics, quantum paraelectrics, and multifferoics, through a combination of advanced experimental techniques and theoretical simulations. The primary goal of her research is to reveal and explore emerging topological chiral states in ferroelectric nanostructures, leveraging advanced experimental methods and 3D polarization reconstruction techniques. These discoveries aim to enable new functionalities, such as tunable multistability and switchable chirality, for innovative technological applications.
A new concept, topological hydrodynamics in ferroelectrics, has been introduced, fundamentally changing the game's rules in how we understand and describe polarization phenomena in these materials. This breakthrough lies at the heart of the comprehensive review Topological Foundations of Ferroelectricity, recently published in the prestigious journal Physics Reports. The review presents a unifying theoretical framework that uses tools from differential topology and fluid dynamics to classify and analyze intricate polarization structures, such as vortices, skyrmions, and Hopfions, in nanostructured ferroelectrics. By bridging electrostatics with the language of incompressible flows, this work paves the way for controlling topological textures in materials, opening exciting prospects for future nanoelectronic and memory technologies. Read the open-access article in Physics Reports (Elsevier): Physics Reports 1110, 1-56 (2025).
Public presentation lecture
Public presentation lecture
October 28th, 2024
Jozef Stefan Institute
Election to the title "Znanstvena sodelavka/Scientific Associate at JSI"
Title: Emergent Functionalities in Ferroelectric Materials
Over the past decade, significant breakthroughs have been made in discovering novel topological polarization structures in nanostructured ferroelectrics. These polar topological domains have attracted considerable interest, not only due to the intriguing physics of topology but also for their potential applications in next-generation nanoelectronics.
This talk reviews the observed polarization topological structures in confined ferroelectrics, with a particular focus on emerging properties such as chirality, which can be controlled by external stimuli.
Sm-doped Pb(Mg1/3Nb2/3)O3–PbTiO3 bulk materials have revealed outstanding ferroelectric and piezoelectric properties due to enhanced local structural heterogeneity. Here, by employing epitaxial thin films, we demonstrate that the Sm-doping enhances the energy storage, piezoelectric, electrocaloric and pyroelectric properties. By using scanning transmission electron microscopy and phase-field modeling, found that these giant properties arise from the increased local structural heterogeneity and strong local electric fields along spontaneous polarization directions facilitating nucleation of slush-like polar structure.
Published in Journal of the American Chemical Society, 146, 47, 32595 (2024)
Movie2_Sm-PMN-PT.mp4
An intriguing feature of nanoscale ferroelectric materials is the emergence of topological polar textures, characterized by complex and stable polarization configurations. Manipulating these textures with external stimuli, such as electric fields, offers potential for advanced nanoelectronics. However, challenges remain, including reliable creation and control of these textures on silicon and with lead-free compounds.
Here we demonstrate epitaxial BaTiO3 nanoislands on silicon with stable center-down polarization domains that can be reversibly switched to center-up domains using an electric field.
Here we report a mechanism wiping out the polarization discontinuity (appearing when antiparallel domains meet) in the uniaxial ferroelectrics possessing low domain wall conductivity. This mechanism consists in forming the specific configuration of the polarization vector field with the mutual domain bifurcation. It creates the characteristic saddle-point domain wall morphology removing the need for the screening charge accumulation and associated conductivity enhancement.
Here we put forth an ingenious design for the ferroelectric domain-based field-effect transistor with stable reversible static negative capacitance. Using a dielectric coating of the ferroelectric capacitor enables the tunability of the negative capacitance improving tremendously the performance of the field-effect transistors.
Quantum Critical SrTiO3-based Ferroelectric
Quantum Critical SrTiO3-based Ferroelectric
Here we investigate the Pb-doped SrTiO3 solid solutions, approaching the pre-critical regions of the phase diagram and study the outcome of the coexistence of quantum fluctuations and thermal motion.
Here we study the polar and nonpolar instabilities in the preformation of ferroelectric transition in Ba-doped SrTiO3 under perturbations, deviating the system from quantum paraelectric toward the classic ferroelectric phase.
Here we devise protocols for realizing control and efficient manipulations of the skyrmions with different chirality in ferroelectric nanodots. Our findings open the route for controlled chirality with potential applications in ferroelectric-based information technologies.
Paradigmatic knotted solitons, Hopfions, that are characterized by topological Hopf invariant, attract an intense attention in the diverse areas of physics ranging from high-energy physics, cosmology and astrophysics to biology, magneto- and hydrodynamics and condensed matter physics. Yet, while being of broad interest, they remain elusive and under-explored. Here we demonstrate that Hopfions emerge as a basic configuration of polarization field in confined ferroelectric nanoparticles. Our findings establish that Hopfions are of fundamental importance for the electromagnetic behavior of the nanocomposits and can result in advanced functionalities of these materials.
Here, we show that the ferroelectric nanodot capacitor hosts a stable two-domain state realizing the static reversible negative capacitance device thus opening routes for the extensive use of the negative capacitance in domain wall-based nanoelectronics.
A method employs a device with a heterostructure as a resonator for electrons of an electrical circuit or for a terahertz electromagnetic wave. The heterostructure comprises at least one dielectric layer and at least one ferroelectric layer. The at least one ferroelectric layer comprises a plurality of ferroelectric polarization domains. The plurality of ferroelectric polarization domains forms a polarization pattern. The polarization pattern is adapted to perform an oscillation with a resonance frequency in a terahertz frequency range. The method comprises functionally coupling the oscillation of the polarization pattern and an oscillation of the electrons of the electrical circuit or of the terahertz electromagnetic wave by the device.
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Institut "Jožef Stefan" Jamova cesta 39, 1000 Ljubljana, Slovenija
e-mail: anna.razumnaya@ijs.si
e-mail: anna.razumnaya@ijs.si
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