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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,
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. To illustrate the utility of
multipoles, I will focus on magnetoelectric multipoles [1], that exist both in real and
momentum space. I will show how they are useful in characterizing both real-space magnetic
skyrmion-like spin textures [2] as well as momentum-space spin textures [3], that result from
e.g., Rashba-like interaction. Notably, such real- and momentum-space spin textures are the
key ingredients in designing spintronic devices. In this context, I will further discuss the
emerging field of orbitronics [4,5], an alternative to spintronics, which relies on the orbital
magnetic moment distribution rather than the spin-magnetic moment distribution in the
reciprocal space.
References:
[1] S. Bhowal and N. A. Spaldin, Phys. Rev. Research 3, 033185 (2021).
[2] S. Bhowal and N. A. Spaldin, Phys. Rev. Lett. (Editors' suggestion) 128, 227204 (2022).
[3] S. Bhowal, S. P. Collins and N. A. Spaldin, Phys. Rev. Lett. 128, 116402 (2022).
[4] S. Bhowal and S. Satpathy, Phys. Rev. B (Rapid Comm.) 101, 121112 (2020).
[5] S. Bhowal and G. Vignale, Phys. Rev. B (Editors' suggestion) 103, 195309 (2021). |