Topological Characterization of Classical Waves: The Topological Origin of Magnetostatic Surface Spin Waves

Title
Topological Characterization of Classical Waves: The Topological Origin of Magnetostatic Surface Spin Waves
Authors
김경환Kei YamamotoGuo Chuan ThiangPhilipp PirroKarin Everschor-SitteEiji Saitoh
Keywords
위상학; 스핀파
Issue Date
2019-05
Publisher
Physical review letters
Abstract
We propose a topological characterization of Hamiltonians describing classical waves. Applying it to the magnetostatic surface spin waves that are important in spintronics applications, we settle the speculation over their topological origin. For a class of classical systems that includes spin waves driven by dipole-dipole interactions, we show that the topology is characterized by vortex lines in the Brillouin zone in such a way that the symplectic structure of Hamiltonian mechanics plays an essential role. We define winding numbers around these vortex lines and identify them to be the bulk topological invariants for a class of semimetals. Exploiting the bulk-edge correspondence appropriately reformulated for these classical waves, we predict that surface modes appear but not in a gap of the bulk frequency spectrum. This feature, consistent with the magnetostatic surface spin waves, indicates a broader realm of topological phases of matter beyond spectrally gapped ones.
URI
http://pubs.kist.re.kr/handle/201004/62287
ISSN
0031-9007
Appears in Collections:
KIST Publication > Article
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