Title: Emergent phenomena in solids and how multipoles help in understanding them

Speaker: Dr. Sayantika Bhowal, ETH, Zurich

Gmeet Link: https://meet.google.com/hxv-kwyi-qrx

Abstract: Understanding and foreseeing novel features of crystalline solids are of immense interest for their advanced functional usage. From a theoretical perspective, predicting material properties is a difficult task, and we only occasionally stumble across or discover new physical properties. In this presentation, I will discuss the "multipole analysis" approach that offers a systematic and potent way to accelerate the search for emerging phenomena in solids. Multipoles have been extensively used in numerous branches of physics, widely ranging from nuclear and particle physics and classical electromagnetism. In condensed matter systems, although relatively less explored, they allow the characterization of the charge, spin, and orbital magnetic moments of electrons within a unified picture. Multipoles enable understanding as well as prediction of material properties that result from complex distributions of charge and magnetization density by providing a quantitative measure of such distributions. In my talk, I will discuss some recent achievements that we made using the multipole concept. Multipoles have been found to be extremely powerful in describing a variety of properties, that range from real and momentum-space magnetic textures [1,2] that play a crucial role in the well-known spintronics as well as in the emerging field of orbitronics [3,4], magnetoelectric effect in correlated insulators [5], unconventional antiferromagnetism with non-relativistic spin splitting (known as altermagnetism) [6], kinetic magnetoelectric effect and non-linear Hall effect in polar metals [7], etc. While some progress has been made, there are still many more open directions to be explored. By filling up these gaps, my future goal is towards establishing the unified multipole description of condensed matter properties, that is not only useful in predicting material properties but also provide platform for designing new materials with advanced functionalities which can be synthesized and characterized in.

References: [1] S. Bhowal and N. A. Spaldin, Phys. Rev. Lett. (Editors' suggestion) 128, 227204 (2022).

[2] S. Bhowal, S. P. Collins and N. A. Spaldin, Phys. Rev. Lett. 128, 116402 (2022).

[3] S. Bhowal and S. Satpathy, Phys. Rev. B (Rapid Comm.) 101, 121112 (2020).

[4] S. Bhowal and G. Vignale, Phys. Rev. B (Editors' suggestion) 103, 195309 (2021).

[5] S. Bhowal and N. A. Spaldin, Phys. Rev. Research 3, 033185 (2021).

[6] S. Bhowal and N. A. Spaldin, arXiv:2212.03756 (2022).

[7] S. Bhowal and N. A. Spaldin, arXiv:2210.02993v1 (2022), Accepted in Annu. Rev. Mater. Res.