Please use this identifier to cite or link to this item: http://repositorio.unicamp.br/jspui/handle/REPOSIP/244245
Type: Artigo
Title: Flat-band ferromagnetism and spin waves in topological Hubbard models
Author: Doretto, R. L.
Goerbig, M. O.
Abstract: We study the flat-band ferromagnetic phase of a topological Hubbard model within a bosonization formalism and, in particular, determine the spin-wave excitation spectrum. We consider a square lattice Hubbard model at 1/4-filling whose free-electron term is the p-flux model with topologically nontrivial and nearly flat energy bands. The electron spin is introduced such that the model either explicitly breaks time-reversal symmetry (correlated flat-band Chern insulator) or is invariant under time-reversal symmetry (correlated flat-band Z(2) topological insulator). We generalize for flat-band Chern and topological insulators the bosonization formalism [R. L. Doretto, A. O. Caldeira, and S. M. Girvin, Phys. Rev. B 71, 045339 (2005)] previously developed for the two-dimensional electron gas in a uniform and perpendicular magnetic field at filling factor nu = 1. We show that, within the bosonization scheme, the topological Hubbard model is mapped to an effective interacting boson model. We consider the boson model at the harmonic approximation and show that, for the correlated Chern insulator, the spin-wave excitation spectrum is gapless while, for the correlated topological insulator, gapped. We briefly comment on the possible effects of the boson-boson (spin-wave-spin-wave) coupling.
We study the flat-band ferromagnetic phase of a topological Hubbard model within a bosonization formalism and, in particular, determine the spin-wave excitation spectrum. We consider a square lattice Hubbard model at 1/4-filling whose free-electron term is the p-flux model with topologically nontrivial and nearly flat energy bands. The electron spin is introduced such that the model either explicitly breaks time-reversal symmetry (correlated flat-band Chern insulator) or is invariant under time-reversal symmetry (correlated flat-band Z(2) topological insulator). We generalize for flat-band Chern and topological insulators the bosonization formalism [R. L. Doretto, A. O. Caldeira, and S. M. Girvin, Phys. Rev. B 71, 045339 (2005)] previously developed for the two-dimensional electron gas in a uniform and perpendicular magnetic field at filling factor nu = 1. We show that, within the bosonization scheme, the topological Hubbard model is mapped to an effective interacting boson model. We consider the boson model at the harmonic approximation and show that, for the correlated Chern insulator, the spin-wave excitation spectrum is gapless while, for the correlated topological insulator, gapped. We briefly comment on the possible effects of the boson-boson (spin-wave-spin-wave) coupling.
Subject: Hubbard, Modelo de
Hall, Efeito quântico de
Ferromagnetismo
Country: Estados Unidos
Editor: American Physical Society
Citation: Flat-band Ferromagnetism And Spin Waves In Topological Hubbard Models. Amer Physical Soc, v. 92, p. DEC-2015.
Rights: aberto
Identifier DOI: 10.1103/PhysRevB.92.245124
Address: https://journals.aps.org/prb/abstract/10.1103/PhysRevB.92.245124
Date Issue: 2015
Appears in Collections:IFGW - Artigos e Outros Documentos

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