Quantum phase transition triggering magnetic BICs in graphene

Abstract

Graphene hosting a pair of collinear adatoms in the phantom atom configuration has pseudogap with cubic scaling on energy, $\Delta \propto |\epsilon {|}^3$ 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. In this Letter, we explore the effects of non-local coupling characterized by the Fano factor of interference $q_0,$ 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 $q_0<q_{c1}$ (critical point) a mixed pseudogap $\Delta \propto |\epsilon |,|\epsilon {|}^2$ appears yielding a phase with spin-degenerate BICs; ii) near $q_0=q_{c1}$ when $\Delta \propto |\epsilon {|}^2$ the system undergoes a quantum phase transition in which the new phase is characterized by magnetic BICs and iii) at a second critical value $q_0>q_{c2}$ the cubic scaling of the pseudogap with energy $\Delta \propto |\epsilon {|}^3$ characteristic to the phantom atom configuration is restored and the phase with non-magnetic 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 quantum phase transition resulting from the competition between the states characterized by spin-degenerate and magnetic BICs.

References in corpus (7)

• The electronic properties of graphene
• Localized Spins on Graphene
• Zero-field Kondo splitting and quantum-critical transition in double quantum dots
• Fermionic statistics suppresses Fano resonances
• Tunable Bound States in Continuum by Optical Frequency
• Thermal dependence of the zero-bias conductance through a nanostructure
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Cited by in corpus (6)

• Spin Manipulation in Graphene by Chemically-Induced Sublattice Pseudospin Polarization
• Encrypting Majorana Fermions-qubits as Bound States in the Continuum
• Decay of bound states in the continuum of Majorana fermions induced by vacuum fluctuations: Proposal of qubit technology
• Unveiling Majorana Quasiparticles by a Quantum Phase Transition: Proposal of a Current Switch
• Antibonding Ground state of Adatom Molecules in Bulk Dirac Semimetals
• Solvable model of bound states in the continuum (BIC) in one dimension