Direct visualization of magnetic domains and moiré magnetism in twisted 2D magnets

Abstract

Imaging twisty magnets Twisting monolayers of graphene with respect to each other has led to a number of unusual correlated states. This approach has inspired researchers to try their hand at twisting two-dimensional (2D) magnets, but such experiments have proven a difficult challenge. Song et al . made structures out of layers of the 2D magnet chromium triiodide with a small twist angle (see the Perspective by Lado). Using nitrogen vacancy centers in diamond as a magnetometer, the authors imaged the magnetic domains in both twisted monolayer and twisted trilayer structures. For twisted trilayers, a periodic pattern of ferromagnetic and antiferromagnetic domains was revealed. —JS

Electronic properties of twisted multilayer graphene

“…[34][35][36][37][38][39][40][41] as well as the recent review [42] and references therein). These explorations have also inspired researchers to extendedly apply the twist approach to other physical systems, e.g., magnetic 2D materials [43][44][45][46] and photonic layered structures [47][48][49][50]. In overall, the properties of those systems are definitely dependent of their constituting layers and importantly, can be tuned by varying their twist angle, similar to those observed in TBLG.…”

Magnon corner states in twisted bilayer honeycomb magnets

“…Our theory is immediately testable considering rapid experimental progresses in 2D twisted magnets [94][95][96]. Monolayer Chromium triiodide (CrI 3 ) is a 2D ferromagnet with honeycomb lattice [103].…”

“…Meanwhile, researchers have turned their attention to twisted bilayer honeycomb magnets (TBHMs) analogous to twisted bilayer graphene and theoretically study moiré magnons in TBHMs [91][92][93]. Very recently, moiré magnetism has been experimentally reported in twisted bilayer CrI 3 [94][95][96]. Inspired by the recent theoretical and experimental developments in twisted 2D magnets, it is tempting to ask that whether higher-order topological magnon insulators can occur in TBHMs.…”

Impurity-induced excitations in twisted topological van der Waals superconductors

“…Artificial van der Waals topological superconductors, and moire heterostructures in general, display two length scales, the original lattice constant and the emergent moire length [31][32][33][34][35] . The existence of a moire pattern leads to a superconducting state with an associated moire electronic structure, and more importantly, a spatially modulated structure directly inherited from the moire pattern 36,37 . In particular, atomic defects in twodimensional materials including substitutional elements and vacancies have a relevant length scale stemming from the microscopic lattice constant [38][39][40][41][42] , and therefore can give rise to a rich interplay with the moire length.…”