Band Structure Topology and Spin Transport in Magnon Systems
Thesis Defense
2:00 pm –
3:30 pm
Jorgensen Hall
Contact:
Physics Department, (402) 472-2770, paoffice@unl.edu
Bo Li will present his thesis defense, “Band Structure Topology and Spin Transport in Magnon Systems.” This event will be streamed live without an audience, in closed session with Zoom.
Join Zoom Meeting: https://us04web.zoom.us/j/6373131440?pwd=SkpjQlowN3BIbFlRRWVUcHIrS2ptZz09
Meeting ID: 637 313 1440
Abstract:
As the spin excitation quanta in magnetic materials, the magnon is at the heart of the spintronics research, as it plays a key role in magnetic dynamics, energy and spin transport, and even the determination of the ground state. This thesis dissertation will present results on band-structure topology and transport properties of magnons in both collinear and noncollinear magnets. Inspired by the great success of topological insulators, exploring magnon topology can unveil the topological nature of Bosonic particles and widen the zoo of topological materials, thus bringing new opportunities for technical application. We propose a three-dimensional magnon topological insulator model protected by sublattice chiral symmetries, which shows the possibility of realizing a surface Dirac cone in a magnon system. On the other hand, magnons can mediate angular momentum transport with low dissipation due to the absence of Joule heating. Here, we explore the spin Nernst effect, a transverse spin current driven by a temperature gradient, in noncollinear magnetic systems by developing a new linear response theory. The theory will be applied to frustrated noncollinear antiferromagnets, antiferromagnetic skyrmion crystals, and an antiferromagnetic magnon topological insulator model. In particular, the antiferromagnetic magnon topological insulator model is featured with unconventional Landau levels, which further enriches the magnon topology study. Moreover, we find magnons do not just
facilitate spin transport but also are able to accumulate nonequilibrium net spin density in a sample under the driving of a temperature gradient. The latter effect is a magnon version of the Edelstein effect and can be also analyzed by the aforementioned linear response theory. Such an effect can be ideally realized in 2D and 3D noncollinear antiferromagnets that have a compensating ground state.
Join Zoom Meeting: https://us04web.zoom.us/j/6373131440?pwd=SkpjQlowN3BIbFlRRWVUcHIrS2ptZz09
Meeting ID: 637 313 1440
Abstract:
As the spin excitation quanta in magnetic materials, the magnon is at the heart of the spintronics research, as it plays a key role in magnetic dynamics, energy and spin transport, and even the determination of the ground state. This thesis dissertation will present results on band-structure topology and transport properties of magnons in both collinear and noncollinear magnets. Inspired by the great success of topological insulators, exploring magnon topology can unveil the topological nature of Bosonic particles and widen the zoo of topological materials, thus bringing new opportunities for technical application. We propose a three-dimensional magnon topological insulator model protected by sublattice chiral symmetries, which shows the possibility of realizing a surface Dirac cone in a magnon system. On the other hand, magnons can mediate angular momentum transport with low dissipation due to the absence of Joule heating. Here, we explore the spin Nernst effect, a transverse spin current driven by a temperature gradient, in noncollinear magnetic systems by developing a new linear response theory. The theory will be applied to frustrated noncollinear antiferromagnets, antiferromagnetic skyrmion crystals, and an antiferromagnetic magnon topological insulator model. In particular, the antiferromagnetic magnon topological insulator model is featured with unconventional Landau levels, which further enriches the magnon topology study. Moreover, we find magnons do not just
facilitate spin transport but also are able to accumulate nonequilibrium net spin density in a sample under the driving of a temperature gradient. The latter effect is a magnon version of the Edelstein effect and can be also analyzed by the aforementioned linear response theory. Such an effect can be ideally realized in 2D and 3D noncollinear antiferromagnets that have a compensating ground state.