Dynamical centrosymmetry breaking — A novel mechanism for second harmonic generation in graphene

Carvalho, David N.; Marini, Andrea; Biancalana, Fabio

doi:10.1016/j.aop.2016.11.016

Cited by 7 publications

(8 citation statements)

References 26 publications

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“…( 16) is plotted in units of the pulse-normalised frequency ω/ω 0 . The linear model shows the well-known strong third harmonic observed in graphene, as well as small second-harmonic peaks previously reported to exist due to light-induced dynamical centrosymmetry breaking [19,24]. As expected, the explicit centrosymmetry breaking of the lattice arrangement as depicted in Fig.…”

Section: A Role Of the K • P Expansionsupporting

confidence: 82%

“…The output current J has, perhaps surprisingly, both non-vanishing longitudinal and transverse components to the electric field, polarised along Θ. The present machinery has been previously applied to both gapless and gapped graphene monolayers in [19,24]. The gapless case presented a straightforward analysis: only current along the same di-FIG.…”

Section: A Role Of the K • P Expansionmentioning

confidence: 96%

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Role of Anisotropy in Nonlinear Harmonic Generation Across TMD Monolayers

Carvalho¹,

Biancalana²

2020

Preprint

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Section: A Role Of the K • P Expansionsupporting

confidence: 82%

Section: A Role Of the K • P Expansionmentioning

confidence: 96%

Role of Anisotropy in Nonlinear Harmonic Generation Across TMD Monolayers

Carvalho¹,

Biancalana²

2020

Preprint

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“…The full Dirac equation ( 1) can be recast in a more transparent set of equations, akin to the Bloch equations of a two-level system -the Dirac-Bloch equations (DBEs) -which are derived and shown for the case of massless Dirac fermions in Ref. 11 . When generalised to the massive case, they take the form:…”

Section: The Massive Dirac-bloch Equationsmentioning

confidence: 99%

“…However, intense and ultrashort pulses provide a regime where odd harmonics interfere generating even harmonics, once gapped. Besides, the dynamical centrosymmetry breaking mechanism, a field-driven effect that globally displaces the electronic dispersion and breaks the centrosymmetry k ↔ −k (and consequently r ↔ −r in direct space), has been shown to predict second-harmonic generation in freestanding, ungapped graphene 11 . Gapping the spectrum renders the electrons massive and, as will be demonstrated, induces a Berry phase in the carrier dynamics.…”

Section: Introductionmentioning

confidence: 99%

“…Gapping the spectrum renders the electrons massive and, as will be demonstrated, induces a Berry phase in the carrier dynamics. Such a phase leads to interesting qualitatively different optical behaviour which is studied by extending the Dirac-Bloch equations and their framework, previously applied to massless Dirac fermions (namely monolayer graphene) [11][12][13] , to incorporate a gapped Dirac spectrum.…”

Section: Introductionmentioning

confidence: 99%

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Nonlinear optical effects of opening a gap in graphene

2018

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Graphene possesses remarkable electronic, optical and mechanical properties that have taken the research of two-dimensional relativistic condensed matter systems to prolific levels. However, the understanding of how its nonlinear optical properties are affected by relativistic-like effects has been broadly uncharted. It has been recently shown that highly-nontrivial currents can be generated in free-standing samples, notably leading to the generation of even harmonics. Since graphene monolayers are centrosymmetric media, for which such harmonic generation is deemed inaccessible, this light-driven phenomenon is both startling and promising. More realistically, graphene samples are often deposited on a dielectric substrate, leading to additional intricate interactions. Here, we present a treatment to study this instance by gapping the spectrum and we show this leads to the appearance of a Berry phase in the carrier dynamics. We analyse the role of such a phase in the generated nonlinear current and conclude that it suppresses odd-harmonic generation. The pump energy can be tuned to the energy gap to yield interference among odd harmonics mediated by interband transitions, allowing even harmonics to be generated. Our results and general methodology pave the way for understanding the role of gap-opening physical factors in the nonlinear optics of hexagonal two-dimensional lattices.arXiv:1710.04581v1 [cond-mat.mes-hall]

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Generation of half-integer harmonics and efficient THz-to-visible frequency conversion in strained graphene

Ornigotti

Biancalana

2021

APL Photonics

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We study the generation of harmonics from graphene under the influence of an artificial magnetic field, generated via bending of a graphene flake. We show how the Landau level structure induced by the pseudomagnetic field breaks the centrosymmetry of graphene, thus allowing the generation of even harmonics. We also show that depending on the impinging pulse duration, the nonlinear signal does not only contain the integer harmonics of the impinging pulse but also its half-integer ones due to the peculiar square-root-like nature of Landau levels in graphene.

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Dynamical centrosymmetry breaking — A novel mechanism for second harmonic generation in graphene

Cited by 7 publications

References 26 publications

Role of Anisotropy in Nonlinear Harmonic Generation Across TMD Monolayers

Role of Anisotropy in Nonlinear Harmonic Generation Across TMD Monolayers

Nonlinear optical effects of opening a gap in graphene

Generation of half-integer harmonics and efficient THz-to-visible frequency conversion in strained graphene

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