Topological Hybrids of Magnons and Magnon Bound Pairs

Abstract

We consider quantum condensed matter systems without particle-number conservation. Since the particle number is not a good quantum number, states belonging to different particle-number sectors can hybridize, which causes topological anticrossings in the spectrum. The resulting spectral gaps support chiral edge excitations whose wavefunction is a superposition of states in the two hybridized sectors. This situation is realized in fully saturated spin-anisotropic quantum magnets without spin conservation, in which single magnons hybridize with magnon bound pairs, i.e., two-magnon bound states. The resulting chiral edge excitations are exotic composites that carry mixed spin-multipolar character, inheriting spin-dipolar and spin-quadrupolar character from their single-particleness and two-particleness, respectively. In contrast to established topological magnons, the topological effects discussed here are of genuine quantum mechanical origin and vanish in the classical limit. We discuss implications for both intrinsic anomalous Hall-type transport and beyond-spintronics computation paradigms. We conclude that fully polarized quantum magnets are a promising platform for topology caused by hybridizations between particle-number sectors, complementing the field of ultracold atoms working with a conserved number of particles.

27 pages, 18 figures

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Cited by in corpus (10)

• Topological Phases in Magnonics
• Thermal Hall effect incorporating magnon damping in localized spin systems
• Thermal Hall Effect of Magnons from Many-Body Skew Scattering
• Two-particle bound states on a lattice
• Ground state properties of the Heisenberg-compass model on the square lattice
• Large Thermal Hall Effect in MnPS${}_3$
• Magnon bands and transverse transport in a proposed two-dimensional $C{u}_2{F}_5$ ferrimagnet
• Intrinsic Thermal Hall Effect in Mott Insulators
• Longitudinal magnons in large-$S$ easy-axis magnets
• Tunable multi-magnon Floquet topological edge states