Polar Topological Defects in Ferroelectric Nanostructures: Novel Features and Phenomena

About twenty years ago, electrical topological defects were predicted in ferroelectric nanostructures [1-3]. These fascinating objects are now forming one active and exciting research field, since they have the potential to revolutionize technologies but also yield striking phenomena (see, <i>e.g.</i>, Refs. [4-7] and references therein).<br/> <br/>The aim of this Talk is to reveal and explain, via the use of first-principle-based atomistic effective Hamiltonians and state-of-the-art experimental growth and characterization techniques, the emergence of novel features, all associated with polar topological states. This includes:<br/>Their activation by THz pulses and twisted light [8-10],<br/>Their role in creating magnetism in nominal non-magnetic systems [11],<br/>The systematic control of their motions across thin films [10,12,13],<br/>The unusual lattice vibrations and soft modes responsible for their condensation [14,15],<br/>The transitions between different topological states [16-20], and<br/>The occurrence of novel phases and phenomena, such as polar solitons in low-dimensional multiferroics [21], quantum-induced dipolar liquid states and quantum criticality [22] and electrical hopfions [23].<br/> <br/>The authors at Arkansas thank the Vannevar Bush Faculty Fellowship (VBFF) from the Department of Defense, the MonArk NSF Quantum Foundry supported by the National Science Foundation Q-AMASE-I Program under NSF Award No.DMR-1906383, the ARO Grants No. W911NF-21-1-011 and W911NF-21-2-0162 (ETHOS), the DARPA Grant No. HR0011727183-D18AP00010 (TEE Program), and the ONR Grant N00014-21-1-2086. The research at University of New South Wales (UNSW) is supported by DARPA Grant No. HR0011727183-D18AP00010 (TEE Program), partially supported by the Australian Research Council Centre of Excellence in Future Low-Energy Electronics Technologies (project number CE170100039) and funded by the Australian Government.<br/> <br/>References:<br/>[1] Ivan I. Naumov <i>et al.</i>, Nature (London) 432, 737 (2004).<br/>[2] I. Kornev <i>et al.</i>, Physical Review Letters 93, 196104 (2004).<br/>[3] H. Fu and L. Bellaiche, Physical Review Letters 91<b>,</b> 257601 (2003).<br/>[4] Vivasha Govinden <i>et al.</i>, Nature Materials 22, 553-561 (2023).<br/>[5] Javier Junquera, <i>et al.</i>, Reviews of Modern Physics 95, 025001 (2023).<br/>[6] Lu Han <i>et al.</i>, Nature 603, 7899 (2022).<br/>[7] Shuai Yuan <i>et al.</i>, Physical Review Letters 130, 226801 (2023).<br/>[8] Peng Chen <i>et al.</i>, Physical Review B 107, L060101 (2023).<br/>[9] Sergey Prosandeev <i>et al.</i>, Advanced Electronic Materials, 2200808 (2022).<br/>[10] Lingyuan Gao <i>et al.</i>, under review. <br/>[11] Lingyuan Gao <i>et al.</i>, Physical Review Letters, in press.<br/>[12] Sukriti Mantri <i>et al.</i>, under review. <br/>[13] Sergei Prokhorenko <i>et al.</i>, under review.<br/>[14] Suyas Rijal <i>et al.</i>, under review.<br/>[15] Maxim A. Makeev <i>et al.</i>, in preparation.<br/>[16] Vivasha Govinden <i>et al.</i>, Physical Review Materials 7, L011401 (2023). <br/>[17] Vivasha Govinden <i>et al.</i>, Physical Review Materials 5, 124205 (2021).<br/>[18] Y. Nahas <i>et al.</i>, Nature Communications 11, 5779 (2020).<br/>[19] Qi Zhang <i>et al.</i>, Advanced Functional Materials 1808573 (2019).<br/>[20] Qi Zhang <i>et al.</i>, Advanced Materials 29,1702375 (2017).<br/>[21] Vivasha Govinden <i>et al.</i>, Nature Communications 14, 4178 (2023).<br/>[22] W. Luo <i>et al.</i>, under review. <br/>[23] Suyash Rijal <i>et al.</i>, in preparation.