Research Denis Sabani

Abstract

Further technological advance of our modern society will critically depend on novel, all-in-one materials, able to couple magnetic, elastic, and electronic degrees of freedom in a controllable fashion. Atomically-thin 2D materials may be just what is needed, exhibiting a range of advanced properties, tunable by stretching, bending, gating, and/or heterostructuring. With advent of magnetism in 2D materials (only since 2017), tailoring their multifunctional behavior is at its prime potential. Magnetism in 2D materials is quite special, since any incurred symmetry change (with e.g. bending) affects magnetic interactions and causes adjacent magnetic moments to misalign, owing to strong emergent chirality, comparable to usual aligning interactions. Chiral interactions lead to observable nontrivial magnetic textures, such as skyrmions, and cause entirely different behavior of dynamic excitations (magnons), both of which bear documented technological promise. Symmetry breaking that causes chirality is also accompanied by local electric field, so that chiral magnetism and electric polarization in a 2D material are effectively coupled. This project is devoted to understanding of that coupling, and its response to standard manipulations within the realm of 2D materials, that will enable tailoring of chiral magneto-electronics practically at will, for actively and broadly tunable technology very sensitive to electric, magnetic, optical or mechanical stimuli.

Researcher(s)

• Promoter: Milosevic Milorad
• Fellow: Sabani Denis

Research team(s)

• Condensed Matter Theory

Project type(s)

• Research Project

Abstract

It is well known that magnetic exchange interaction drives the behavior of magnetic materials, making them ferromagnetic (positive interaction, spins parallel) or antiferromagnetic (negative interaction, spins antiparallel). It is far less obvious that there exist components of exchange interaction that lead to chiral magnetism, i.e. causing the adjacent spins to assume orthogonal mutual ordering. Dzyaloshinskii-Moriya interaction (DMI) is one such interaction, first identified in the 60's, but it was only the recent observation of skyrmion lattices that instigated its further fundamental research and technological applications. DMI can only arise in systems that lack inversion symmetry and host strong spin-orbit coupling, a condition that is met in few bulk materials, and at interfaces of specifically designed magnetic heterostructures. In 2017, magnetic ordering was also observed in 2D materials, CrI3 being the first. There, magnetic atoms (Cr) are in direct bonding with non-magnetic atoms with strong spin-orbit coupling (I). Therefore DMI must be intrinsically present but is cancelled out in a perfect crystalline lattice so there is no apparent DMI, unless symmetry is broken (at the edges, defects, grain boundaries etc.). What are the microscopic mechanisms to awaken such a dormant DMI, how significant it can be, and how to tailor its release and the corresponding spin textures as a function of temperature and magnetic field, are the overarching themes in this project.

Researcher(s)

• Promoter: Milosevic Milorad
• Fellow: Sabani Denis

Research team(s)

• Condensed Matter Theory

Project type(s)

• Research Project