Topological magnons in ferromagnetic Kitaev-Heisenberg model on CaVO lattice

Abstract

A number of first order topological phases are found to emerge in the ferromagnetic Kitaev-Heisenberg model on square-octagon lattice in the presence of Dzyaloshinskii-Moriya interaction. Heisenberg and Kitaev terms have been considered on nearest and next-nearest neighbor bonds in a variety of ways. Both isotropic and anisotropic couplings are taken into account. Topological phases are characterized by Chern numbers for the distinct magnon bands as well as the number of modes for topologically protected gapless magnon edge states. Band structure, dispersion relation along the high-symmetric points of first Brillouin zone, density of states and thermal Hall conductance have been evaluated for every phase. Phase diagrams have been constructed. Topological phase transition is also noted in the parameter space.

Magnetic field induced topological nodal-lines in triplet excitations of frustrated antiferromagnet CaV$_4$O$_9$

“…This difference attributes to the fact that AFM ground state breaks the full symmetry of the Heisenberg Hamiltonian, while the singlet ground states in this study do not. Emergence of multiple topological phases in irradiated tightbinding and FM Kitaev-Heisenberg models on this lattice is noted before 25,26 . The effect of DMI cannot be registered either in POT or BOT because of the fact that, n (S n × S n+1 ) z vanishes identically over a plaquette and bond, when S is expressed in terms of either plaquette or bond operators, respectively.…”