Quantum phase transition triggering magnetic bound states in the continuum in graphene

Graphene hosting a pair of collinear adatoms in the phantom atom configuration has density of states vanishing in the vicinity of the Dirac point which can be described in terms of the pseudogap scaling as cube of the energy, Δ∝|ɛ|3, which leads to the appearance of spin-degenerate bound states in t...

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Main Authors: Kristinsson, Kristinn, Shelykh, Ivan A., Guessi, L. H., Marques, Y., Machado, R. S., Ricco, L. S., Figueira, M. S., de Souza, M., Seridonio, A. C.
Other Authors: School of Physical and Mathematical Sciences
Format: Article
Language:English
Published: 2016
Online Access:https://hdl.handle.net/10356/81922
http://hdl.handle.net/10220/39694
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Institution: Nanyang Technological University
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spelling sg-ntu-dr.10356-819222023-02-28T19:31:04Z Quantum phase transition triggering magnetic bound states in the continuum in graphene Kristinsson, Kristinn Shelykh, Ivan A. Guessi, L. H. Marques, Y. Machado, R. S. Ricco, L. S. Figueira, M. S. de Souza, M. Seridonio, A. C. School of Physical and Mathematical Sciences Graphene hosting a pair of collinear adatoms in the phantom atom configuration has density of states vanishing in the vicinity of the Dirac point which can be described in terms of the pseudogap scaling as cube of the energy, Δ∝|ɛ|3, which leads to the appearance of spin-degenerate bound states in the continuum (BICs) [Phys. Rev. B 92, 045409 (2015)]. In the case when adatoms are locally coupled to a single carbon atom the pseudogap scales linearly with energy, which prevents the formation of BICs. Here, we explore the effects of nonlocal coupling characterized by the Fano factor of interference q0, tunable by changing the slope of the Dirac cones in the graphene band structure. We demonstrate that three distinct regimes can be identified: (i) for q0<qc1 (critical point) a mixed pseudogap Δ∝|ɛ|,|ɛ|2 appears yielding a phase with spin-degenerate BICs; (ii) near q0=qc1 when Δ∝|ɛ|2 the system undergoes a quantum phase transition (QPT) in which the new phase is characterized by magnetic BICs, and (iii) at a second critical value q0>qc2 the cubic scaling of the pseudogap with energy Δ∝|ɛ|3 characteristic to the phantom atom configuration is restored and the phase with nonmagnetic BICs is recovered. The phase with magnetic BICs can be described in terms of an effective intrinsic exchange field of ferromagnetic nature between the adatoms mediated by graphene monolayer. We thus propose a new type of QPT resulting from the competition between two ground states, respectively characterized by spin-degenerate and magnetic BICs. Published version 2016-01-13T07:40:41Z 2019-12-06T14:43:08Z 2016-01-13T07:40:41Z 2019-12-06T14:43:08Z 2015 Journal Article Guessi, L. H., Marques, Y., Machado, R. S., Kristinsson, K., Ricco, L. S., Shelykh, I. A., et al. (2015). Quantum phase transition triggering magnetic bound states in the continuum in graphene. Physical Review B, 92, 245107-. 1098-0121 https://hdl.handle.net/10356/81922 http://hdl.handle.net/10220/39694 10.1103/PhysRevB.92.245107 en Physical Review B © 2015 American Physical Society. This paper was published in Physical Review B and is made available as an electronic reprint (preprint) with permission of American Physical Society. The published version is available at: [http://dx.doi.org/10.1103/PhysRevB.92.245107]. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper is prohibited and is subject to penalties under law. 6 p. application/pdf
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description Graphene hosting a pair of collinear adatoms in the phantom atom configuration has density of states vanishing in the vicinity of the Dirac point which can be described in terms of the pseudogap scaling as cube of the energy, Δ∝|ɛ|3, which leads to the appearance of spin-degenerate bound states in the continuum (BICs) [Phys. Rev. B 92, 045409 (2015)]. In the case when adatoms are locally coupled to a single carbon atom the pseudogap scales linearly with energy, which prevents the formation of BICs. Here, we explore the effects of nonlocal coupling characterized by the Fano factor of interference q0, tunable by changing the slope of the Dirac cones in the graphene band structure. We demonstrate that three distinct regimes can be identified: (i) for q0<qc1 (critical point) a mixed pseudogap Δ∝|ɛ|,|ɛ|2 appears yielding a phase with spin-degenerate BICs; (ii) near q0=qc1 when Δ∝|ɛ|2 the system undergoes a quantum phase transition (QPT) in which the new phase is characterized by magnetic BICs, and (iii) at a second critical value q0>qc2 the cubic scaling of the pseudogap with energy Δ∝|ɛ|3 characteristic to the phantom atom configuration is restored and the phase with nonmagnetic BICs is recovered. The phase with magnetic BICs can be described in terms of an effective intrinsic exchange field of ferromagnetic nature between the adatoms mediated by graphene monolayer. We thus propose a new type of QPT resulting from the competition between two ground states, respectively characterized by spin-degenerate and magnetic BICs.
author2 School of Physical and Mathematical Sciences
author_facet School of Physical and Mathematical Sciences
Kristinsson, Kristinn
Shelykh, Ivan A.
Guessi, L. H.
Marques, Y.
Machado, R. S.
Ricco, L. S.
Figueira, M. S.
de Souza, M.
Seridonio, A. C.
format Article
author Kristinsson, Kristinn
Shelykh, Ivan A.
Guessi, L. H.
Marques, Y.
Machado, R. S.
Ricco, L. S.
Figueira, M. S.
de Souza, M.
Seridonio, A. C.
spellingShingle Kristinsson, Kristinn
Shelykh, Ivan A.
Guessi, L. H.
Marques, Y.
Machado, R. S.
Ricco, L. S.
Figueira, M. S.
de Souza, M.
Seridonio, A. C.
Quantum phase transition triggering magnetic bound states in the continuum in graphene
author_sort Kristinsson, Kristinn
title Quantum phase transition triggering magnetic bound states in the continuum in graphene
title_short Quantum phase transition triggering magnetic bound states in the continuum in graphene
title_full Quantum phase transition triggering magnetic bound states in the continuum in graphene
title_fullStr Quantum phase transition triggering magnetic bound states in the continuum in graphene
title_full_unstemmed Quantum phase transition triggering magnetic bound states in the continuum in graphene
title_sort quantum phase transition triggering magnetic bound states in the continuum in graphene
publishDate 2016
url https://hdl.handle.net/10356/81922
http://hdl.handle.net/10220/39694
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