Noncollinear magnetic ordering in the Shastry-Sutherland Kondo lattice model: Insulating regime and the role of Dzyaloshinskii-Moriya interaction

Abstract

We investigate the necessary conditions for the emergence of complex, noncoplanar magnetic configurations in a Kondo lattice model with classical local moments on the geometrically frustrated Shastry-Sutherland lattice and their evolution in an external magnetic field. We demonstrate that topologically nontrivial spin textures, including a new canted flux state, with nonzero scalar chirality arise dynamically from realistic short-range interactions. Our results establish that a finite Dzyaloshinskii-Moriya (DM) interaction is necessary for the emergence of these novel magnetic states when the system is at half filling, for which the ground state is insulating. We identify the minimal set of DM vectors that are necessary for the stabilization of chiral magnetic phases. The noncoplanarity of such structures can be tuned continually by applying an external magnetic field. This is the first part in a series of two papers; in the following paper the effects of frustration, thermal fluctuations, and magnetic field on the emergence of novel noncollinear states at metallic filling of itinerant electrons are discussed. Our results are crucial in understanding the magnetic and electronic properties of the rare-earth tetraboride family of frustrated magnets with separate spin and charge degrees of freedom.

Topological Hall effect in the Shastry-Sutherland lattice

“…Further, the use of an external Zeeman field enhances the possibility of having noncoplanar phases significantly. Previously, we have shown that the Kondo lattice model on the SS lattice exhibits noncoplanar and noncollinear ground states over a wide range of parameters [46][47][48]. In this work, we aim to thoroughly study the effect of all the competing interactions in stabilizing the noncoplanar phases and investigate the transport properties of itinerant electrons on this lattice.…”

Topological excitations in quasi two-dimensional quantum magnets with weak interlayer interactions

“…Here we present the results of our investigation of topological magnons in the recently proposed flux state, that is stabilised by DMI perpendicular to the lattice plane in the SS lattice [58].In presence of in plane DMI, this evolves to the canted flux state -the resulting magnon bands in an external longitudinal magnetic field, carry non-zero Chern numbers that determine the topological character of the magnon bands. Varying the different components of the DMI result in a sequence of band topological transitions where the Chern number for the magnon bands change over a wide range of possible values.…”

“…The rare-earth tetraborides are the material realization for frustrated SS-lattices because the antiferromagnetic Heisenberg-interactions on the dimer and axial bonds are nearly equal (J ≈ J ) [55,56,57]. Shahzad et al [58] show that for a classical spin systems in RB 4 , crystal-symmetry allowed perpendicular DMI on the axial bond gives rise to coplanar flux state (see Fig. 1.1(b)).…”

“…of quantum magnets with varying interactions and lattice structures as well as the ability to control the number of quantized excitations with an external magnetic field make them ideal for exploring novel magnetic phases. Geometrically frustrated quantum magnets are particulalry promising in realizing and controlling topologically non-trivial spin textures [179,180,58,181,182,183]. The interplay between competing interactions, geometric frustration and external magnetic field result in a wide variety of magnetic phases that are not commonly observed in their non-frustrated counterparts.…”

“…Since DMI is ubiquitous in all of these materials, it is natural to supplement the canonical SS model with DMI. This results in an even richer variety of magnetic orderings including collinear, coplanar and non-coplanar spin configurations, several of which host topological magnons [58,189]. Previous studies of topological magnons for the SS lattice were restricted to the dimer [1] and the ferro-magnetic phases [54].…”