Strain-Induced Topological Magnon Phase Transitions: Applications to Kagome-Lattice Ferromagnets

Abstract

A common feature of topological insulators is that they are characterized by topologically invariant quantity such as the Chern number and the ${\mathbb{Z}}_2$ index. This quantity distinguishes a nontrivial topological system from a trivial one. A topological phase transition may occur when there are two topologically distinct phases, and it is usually defined by a gap closing point where the topologically invariant quantity is ill-defined. In this paper, we show that the magnon bands in the strained (distorted) kagome-lattice ferromagnets realize an example of a topological magnon phase transition in the realistic parameter regime of the system. When spin-orbit coupling (SOC) is neglected (i.e. no Dzyaloshinskii-Moriya interaction), we show that all three magnon branches are dispersive with no flat band, and there exists a critical point where tilted Dirac and semi-Dirac point coexist in the magnon spectra. The critical point separates two gapless magnon phases as opposed to the usual phase transition. Upon the inclusion of SOC, we realize a topological magnon phase transition point at the critical strain ${\delta }_c=\frac{1}{2}[1-(D/J{)}^2]$, where $D$ and $J$ denote the perturbative SOC and the Heisenberg spin exchange interaction respectively. It separates two distinct topological magnon phases with different Chern numbers for $\delta <{\delta }_c$ and for $\delta >{\delta }_c$. The associated anomalous thermal Hall conductivity develops an abrupt change at ${\delta }_c$, due to the divergence of the Berry curvature in momentum space. The proposed topological magnon phase transition is experimentally feasible by applying external perturbations such as uniaxial strain or pressure.

7 pages, 6 figures. v3 contains revised title and revised interpretation of results. To be published in J. Phys. Condens. Mat. (2018)

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Cited by in corpus (13)

• Magnon thermal Hall effect in kagome antiferromagnets with Dzyaloshinskii-Moriya interactions
• Topological insulators and semimetals in classical magnetic systems
• Topological Phase Transitions of Dirac Magnons in Honeycomb Ferromagnets
• Magnon valley Hall effect in CrI3-based vdW heterostructures
• Twist-induced magnon Landau levels in honeycomb magnets
• Topological Magnon Insulator with a Kekule Bond Modulation
• Time-dependent strain-tuning topological magnon phase transition
• Observation of a flat and extended surface state in a topological semimetal
• Intrinsic Second-Order magnon Thermal Hall Effect
• Exotic topological point and line nodes in the plaquette excitations of a frustrated Heisenberg antiferromagnet on the honeycomb lattice
• High-Field Expansion Approach to Kagome Antiferromagnets with Dzyaloshinskii-Moriya Interactions
• Topology of contact points in Lieb-kagomé model
• Self-consistent renormalized spin-wave theory of magnetic and topological transitions in two-dimensional honeycomb ferromagnets