CHIME — CHirality-Induced dynamics of Magnetization and Electrons

• Applicant: Professor Dr. Jairo Sinova, Ph.D.
• Subject Area: Theoretical Condensed Matter Physics
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 399448442

The proposed research project aims to explore dynamical properties of chiral magnetic systems, which are relevant new materials for possible future device applications. The exponential increase on information storage demand has increased the need to find new paradigms of information storage devices. Currently information storage devices are either volatile (e.g. random access memory) or limited in performance (e.g. hard disk drive). Electric control of magnetization has been the focus for possible applications in the next generation devices that are non-volatile with high performance. A recent breakthrough arising from spin-orbit coupling and broken inversion symmetry, has given rise to new chiral electronic states and new phenomena that are forbidden in symmetric systems. Besides the fundamental interest in understanding these new phenomena, it has been demonstrated that it raises the energy efficiency significantly when manipulating magnetic textures affected by this chirality. Previous research has taken mostly either a top-down or a bottom-up approach. A top-down approach is to observe phenomenology first and then introduce phenomenological terms to describe it, but this does rarely allow microscopic understanding. On the other hand, a bottom-up approach is to carry out a first-principles calculation to make a prediction, but its dependence on system parameters makes it difficult to provide a general understanding. The goal of CHIME is to provide an efficient bridge between the two approaches, by providing theoretical descriptions that are concise, unified, general, and easily accessible to experimentalists. Examples of the target phenomena include spin-orbit torque, motion of topological textures, anisotropic magnetoresistance, and spin waves. We seek a model that is simple but still includes all the core microscopic ingredients, of which the parameters can be used as fitting parameters in experiment as well as be obtained by the first-principles calculations for direct predictability and material design power. In this way, we will be able to raise both microscopic and phenomenological understanding of chiral magnets and find an optimized structure for device applications. Our analytic results will be supported by collaboration with numerical simulations done by other members of my group. Concerning experiments we plan to exploit our fruitful collaboration with the in-house group and other external collaborators in Prague, Cambridge, and Kaiserslautern. We plan to generalize our formalism to other systems of recent interest, such as topological insulators, antiferromagnets, ferrimagnets, and superconducting two-dimensional states at interfaces where spin-orbit coupling and broken symmetry play crucial roles.

• DFG Programme: Research Grants