Flat-band physics in the spin-1/2 sawtooth chain

We consider the strongly anisotropic spin-1/2 XXZ model on the sawtooth-chain lattice with ferromagnetic longitudinal interaction J zz = Δ J and aniferromagnetic transversal interaction J xx = J yy = J > 0. At Δ = −1∕2 the lowest one-magnon excitation band is dispersionless (flat) leading to a ma...

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Bibliographic Details
Published in:The European physical journal. B, Condensed matter physics Condensed matter physics, 2020-08, Vol.93 (8), Article 161
Main Authors: Derzhko, Oleg, Schnack, Jürgen, Dmitriev, Dmitry V., Krivnov, Valery Ya, Richter, Johannes
Format: Article
Language:English
Subjects:
Chains
Complex Systems
Condensed Matter Physics
Ferromagnetism
Fluid- and Aerodynamics
Low temperature
Magnons
Manifolds
Physics
Physics and Astronomy
Regular Article
Solid State Physics
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Summary:We consider the strongly anisotropic spin-1/2 XXZ model on the sawtooth-chain lattice with ferromagnetic longitudinal interaction J zz = Δ J and aniferromagnetic transversal interaction J xx = J yy = J > 0. At Δ = −1∕2 the lowest one-magnon excitation band is dispersionless (flat) leading to a massively degenerate set of ground states. Interestingly, this model admits a three-coloring representation of the ground-state manifold [H.J. Changlani et al., Phys. Rev. Lett. 120 , 117202 (2018)]. We characterize this ground-state manifold and elaborate the low-temperature thermodynamics of the system. We illustrate the manifestation of the flat-band physics of the anisotropic model by comparison with two isotropic flat-band Heisenberg sawtooth chains. Our analytical consideration is complemented by exact diagonalization and finite-temperature Lanczos method calculations. Graphical abstract
ISSN:1434-6028
1434-6036
DOI:10.1140/epjb/e2020-10224-1