Title: Towards a unified theory for the emergent properties of condensed matter systems
Speaker: Dr. Sayantika Bhowal, ETH Zurich
Abstract: Understanding and foreseeing novel and emergent properties of condensed matter systems have been of immense interest in recent times not only in the context of fundamental research but also for their advanced functional usage. While the development of density functional theory has been a breakthrough in the theoretical approaches for a realistic description of solid-state materials, predicting material properties still remains a challenging task. This is partly, related to the absence of any systematic approach to account for the understanding of physical properties in real systems.
In my talk, I will discuss the _"multipole analysis"_ approach that emerges as a systematic and potent way to understand a wide range of physical phenomena in condensed matter systems within a unified framework, and therefore, consequently, also, accelerate the search for emerging phenomena in such systems. The success behind the approach lies in the fact that it allows a complete characterization of the charge and magnetization density of these systems which in turn is responsible for their emergent properties. After introducing the importance of multipole analysis, I will give an overview of the recent advancements in the approach by focusing on its contributions and success in addressing three fundamental problems in physics: finding hidden order [1], understanding and predicting various cross-coupling effects [2], and resolving the ambiguity in the anomalous Hall transport in non-collinear antiferromagnets [3]. Finally, I will discuss some of our recent achievements in pushing this field further by applying the concepts to systems, beyond topologically trivial magnets [4], going beyond spin transport [5,6] as well as manipulating the multipoles in real systems to control the resulting physical properties [7,8] and proposing ways to probe them directly in experiments [7,9]. While noticeable progress has been made so far, there are still many more open directions to explore in the future. Through this progress, we will hopefully be able to establish the multipolar theory as a unified theory for the description of condensed matter systems, which is not only useful in predicting material properties but also provide a platform for designing novel materials with advanced functionalities which can be synthesized and characterized in experiments.
References:
[1] B. B. V. Aken _et. al_., Nature 449, 702-705 (2007); N. A. Spaldin, M. Fiebig, and M. Mostovoy, J. Phys.: Condens. Matter 20, 434203 (2008).
[2] N. A. Spaldin _et. al._, Phys. Rev. B 88, 094429 (2013); H. Watanabe and Y. Yanase, Phys. Rev. B 98, 245129 (2018).
[3] M.-T. Suzuki _et. al._, Phys. Rev. B 95, 094406 (2017) ; M. Kimata _et. al._, Nat. Comm. 12, 5582 (2021).
[4] S. Bhowal and N. A. Spaldin, Phys. Rev. Lett. (Editors' suggestion) 128, 227204 (2022).
[5] S. Bhowal and S. Satpathy, Phys. Rev. B (Rapid Comm.) 101, 121112 (2020).
[6] S. Bhowal and G. Vignale, Phys. Rev. B (Editors' suggestion) 103, 195309 (2021).
[7] S. Bhowal, S. P. Collins and N. A. Spaldin, Phys. Rev. Lett. 128, 116402 (2022).
[8] S. Bhowal and N. A. Spaldin, arXiv:2212.03756 (2022).
[9] S. Bhowal and N. A. Spaldin, Phys. Rev. Research 3, 033185 (2021).