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BCS-BEC crossover and superconductor-insulator transition in Hopf-linked Graphene layers: Hopfene

BCS-BEC crossover and superconductor-insulator transition in Hopf-linked Graphene layers: Hopfene
BCS-BEC crossover and superconductor-insulator transition in Hopf-linked Graphene layers: Hopfene
We have proposed a topological carbon allotrope, named Hopfene, which has three-dimensional (3D) arrays of Hopf-links to bind 2D Graphene layers both horizontally and vertically without forming strong σ bonds between layers. Tight-binding calculations show unique band structures of this crystal, which predicts semi-metal characteristics with the existence of both Weyl and Dirac Fermions depending on the Fermi energy. Here, we have theoretically examined superconductivity of Hopfene based on the attractive Hubbard model. Regardless of its simplicity of the model, we found non-trivial competitions between Hartree–Fock mean-field contributions and Cooper-paring interactions to open semiconductor and superconducting energy gaps, respectively. Consequently, the superconducting order parameters are significantly reduced at every quarterly doping concentration, where the system is in the close vicinity of the quantum critical point, and we found superconductor-insulator transition in the strong coupling limit. Upon doping, we confirmed a classical scenario of a smooth crossover from weak coupling Bardeen-Cooper-Schrieffer (BCS) superconductivity to strong coupling Bose–Einstein Condensation (BEC) of preformed pairs by increasing the interaction strength. We think the proposed Hopfene is a useful platform to investigate the impacts of the topological nature of the Fermi surfaces on the superconductivity and other orders, including charge-density-waves and magnetic orders, and possible quantum phase transitions among them.
1-21
Saito, Shinichi
14a5d20b-055e-4f48-9dda-267e88bd3fdc
Tomita, Isao
e4a78ed2-f525-4fb0-9711-86e2b2dd5587
Saito, Shinichi
14a5d20b-055e-4f48-9dda-267e88bd3fdc
Tomita, Isao
e4a78ed2-f525-4fb0-9711-86e2b2dd5587

Saito, Shinichi and Tomita, Isao (2019) BCS-BEC crossover and superconductor-insulator transition in Hopf-linked Graphene layers: Hopfene. Materials Research Express, 6, 1-21, [106004]. (doi:10.1088/2053-1591/ab4337).

Record type: Article

Abstract

We have proposed a topological carbon allotrope, named Hopfene, which has three-dimensional (3D) arrays of Hopf-links to bind 2D Graphene layers both horizontally and vertically without forming strong σ bonds between layers. Tight-binding calculations show unique band structures of this crystal, which predicts semi-metal characteristics with the existence of both Weyl and Dirac Fermions depending on the Fermi energy. Here, we have theoretically examined superconductivity of Hopfene based on the attractive Hubbard model. Regardless of its simplicity of the model, we found non-trivial competitions between Hartree–Fock mean-field contributions and Cooper-paring interactions to open semiconductor and superconducting energy gaps, respectively. Consequently, the superconducting order parameters are significantly reduced at every quarterly doping concentration, where the system is in the close vicinity of the quantum critical point, and we found superconductor-insulator transition in the strong coupling limit. Upon doping, we confirmed a classical scenario of a smooth crossover from weak coupling Bardeen-Cooper-Schrieffer (BCS) superconductivity to strong coupling Bose–Einstein Condensation (BEC) of preformed pairs by increasing the interaction strength. We think the proposed Hopfene is a useful platform to investigate the impacts of the topological nature of the Fermi surfaces on the superconductivity and other orders, including charge-density-waves and magnetic orders, and possible quantum phase transitions among them.

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More information

In preparation date: 6 June 2019
Accepted/In Press date: 10 September 2019
e-pub ahead of print date: 10 September 2019

Identifiers

Local EPrints ID: 434082
URI: http://eprints.soton.ac.uk/id/eprint/434082
PURE UUID: 9b78d9fa-9377-43e7-88da-c10dbfc01f0f
ORCID for Shinichi Saito: ORCID iD orcid.org/0000-0003-1539-1182

Catalogue record

Date deposited: 11 Sep 2019 16:30
Last modified: 30 Nov 2020 05:01

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