Effective spin-2 quasi-particles at linear dispersive five-fold degenerate points with tunable topological Chern numbers

Cheng, Feng; Wang, Qiang; Zhu, Shi-Liang; Liu, Hui

doi:10.1016/j.physleta.2019.04.016

Cited by 4 publications

(3 citation statements)

References 74 publications

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“…Therefore we expect all of these systems to display mode conversion. We consider here the case of pseudospin-2 Dirac systems [47]. The Hamiltonian that describes massless pseudospin-2 Dirac particles in 2D in a 1D scalar potential U = U (x) has a similar form as Eq.…”

Section: Pseudospin-2 Dirac Equationmentioning

confidence: 99%

Mode conversion and resonant absorption in inhomogeneous materials with flat bands

Kim,

Kim

2022

Preprint

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Mode conversion of transverse electromagnetic waves into longitudinal oscillations and the associated resonant absorption of wave energy in inhomogeneous plasmas is a phenomenon that has been studied extensively in plasma physics. We show that precisely analogous phenomena occur generically in electronic and photonic systems where dispersionless flat bands and dispersive bands coexist in the presence of an inhomogeneous potential or medium parameter. We demonstrate that the systems described by the pseudospin-1 Dirac equation with two dispersive bands and one flat band display mode conversion and resonant absorption in a very similar manner to p-polarized electromagnetic waves in an unmagnetized plasma by calculating the mode conversion coefficient explicitly using the invariant imbedding method. We also show that a similar mode conversion process takes place in many other systems with a flat band such as pseudospin-2 Dirac systems, continuum models obtained for one-dimensional stub and sawtooth lattices, and two-dimensional electron systems with a quadratic band and a nearly flat band. We discuss some experimental implications of mode conversion in flat-band materials and metamaterials.

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Section: Pseudospin-2 Dirac Equationmentioning

confidence: 99%

Mode conversion and resonant absorption in inhomogeneous materials with flat bands

Kim,

Kim

2022

Preprint

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“…A challenging open problem in artificial lattice systems is the design of conical intersections with higher pseudospin values [4]. Although there have been proposals for generalized conical intersections with arbitrary pseudospin [13,14], and pseudospin-2 ones have been considered theoretically [15,16], no realistic system containing a conical intersection with pseudospin higher than one has been demonstrated until now.…”

Section: Introductionmentioning

confidence: 99%

Pseudospin-2 in photonic chiral borophene

et al. 2023

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Pseudospin is an angular momentum degree of freedom introduced in analogy to the real electron spin in the effective massless Dirac-like equation used to describe wave evolution at conical intersections such as the Dirac cones of graphene. Here, we study a photonic implementation of a chiral borophene allotrope hosting a pseudospin-2 conical intersection in its energy–momentum spectrum. The presence of this fivefold spectral degeneracy gives rise to quasiparticles with pseudospin up to ±2. We report on conical diffraction and pseudospin–orbit interaction of light in photonic chiral borophene, which, as a result of topological charge conversion, leads to the generation of highly charged optical phase vortices.

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“…For instance, higher pseudospin Dirac and Weyl quasiparticles have been studied in Refs. [2][3][4]. These quasiparticles, arising in high-degeneracy points, present enhanced Klein tunneling [5], and superscattering regimes [6].…”

mentioning

confidence: 99%

High-degeneracy points protected by site-permutation symmetries

Lima

Ferreira

2020

Phys. Rev. B

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Space group symmetries dictate the energy degeneracy of quasiparticles (e.g., electronic, photonic) in crystalline structures. For spinless systems, there can only be double or triple degeneracies protected by these symmetries, while other degeneracies are usually taken as accidental. In this Letter we show that it is possible to design higher degeneracies exploring site permutation symmetries. These design principles are shown to be satisfied in previously studied lattices, and new structures are proposed with three, four and five degeneracy points for spinless systems. The results are general and apply to different quasiparticle models. Here, we focus on a tight-binding approach for the electronic case as a proof of principle. The resulting high-degeneracy points are protected by the site-permutation symmetries, yielding pseudospin-1 and -2 Dirac fermions. The strategy proposed here can be used to design lattices with high-degeneracy points in electronic (e.g. metal-organic frameworks), photonic, phononic, magnonic and cold-atom systems.

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Effective spin-2 quasi-particles at linear dispersive five-fold degenerate points with tunable topological Chern numbers

Cited by 4 publications

References 74 publications

Mode conversion and resonant absorption in inhomogeneous materials with flat bands

Mode conversion and resonant absorption in inhomogeneous materials with flat bands

Pseudospin-2 in photonic chiral borophene

High-degeneracy points protected by site-permutation symmetries

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