Elusive Dirac magnons: experiment meets theory

by Dr. Ilia Khait

University of Toronto

at Condensed Matter Seminar

Mon, 27 Dec 2021, 11:30
Sacta-Rashi Building for Physics (54), room 207

Abstract

The discovery of massless Dirac electrons in graphene and topological Dirac-Weyl materials has
prompted a broad search for bosonic analogues of such Dirac particles.
Recent experiments have found evidence for Dirac magnons in a two-dimensional CrI3 crystal,
and in a three-dimensional Heisenberg magnet Cu3TeO6.
I will describe the results of an inelastic neutron scattering investigation on a stacked honeycomb lattice magnet CoTiO3,
which is part of a broad family of ilmenite materials.
I will argue that the magnon dispersion relation is well described by a simple magnetic Hamiltonian with strong easy-plane exchange anisotropy. Importantly, a magnon Dirac cone is found along the edge of the 3D Brillouin zone.
However, the simplistic model does not capture the entire picture, therefore I will explain some required modifications.
Lastly, I will present a perturbative formulation which allows generating an effective two-band bosonic model, similar to graphene, to analyze band touchings in bosonic Hamiltonians.
Our results establish CoTiO3 as a model material to study interacting Dirac bosons in a 3D quantum XY magnet, but pose some yet to be resolved intriguing questions.

Created on 22-12-2021 by Meidan, Dganit (dganit)
Updaded on 22-12-2021 by Meidan, Dganit (dganit)