Weyl semimetals in ultrafast laser fields

Nematollahi, Fatemeh; Motlagh, S. Azar Oliaei; Apalkov, Vadym; Stockman, Mark I.

doi:10.1103/physrevb.99.245409

Cited by 21 publications

(7 citation statements)

References 30 publications

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“…A better representation of the detected sign change is shown in Figure b, where the modulation at the temporal overlap ( t = 0 fs) for each probe wavelength is displayed. Recent theoretical calculations of WSM's in ultrafast laser fields [ 47 ] predicted that the fast electron–electron scattering toward the Weyl node happens in the first 10 fs after the pump pulse arrives. Even though this is at the limit of the temporal resolution of the experimental setup, we attribute the sharp peak at the temporal overlap in Figure 3a,b to this ultrafast relaxation, visible in the single traces at selected 715 and 785 nm probe wavelengths in Figure 4a.…”

Section: Resultsmentioning

confidence: 99%

Ultrafast Sub‐100 fs All‐Optical Modulation and Efficient Third‐Harmonic Generation in Weyl Semimetal Niobium Phosphide Thin Films

et al. 2022

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Since their experimental discovery in 2015, Weyl semimetals have generated a large amount of attention due their intriguing physical properties that arise from their linear electron dispersion relation and topological surface states. In particular, in the field of nonlinear (NL) optics and light harvesting, Weyl semimetals have shown outstanding performances and achieved record NL conversion coefficients. In this context, the first steps toward Weyl semimetal nanophotonics are performed here by thoroughly characterizing the linear and NL optical behavior of epitaxially grown niobium phosphide (NbP) thin films, covering the visible to the near‐infrared regime of the electromagnetic spectrum. Despite the measured high linear absorption, third‐harmonic generation studies demonstrate high conversion efficiencies up to 10−4% that can be attributed to the topological electron states at the surface of the material. Furthermore, nondegenerate pump–probe measurements with sub‐10 fs pulses reveal a maximum modulation depth of ≈1%, completely decaying within 100 fs and therefore suggesting the possibility of developing all‐optical switching devices based on NbP. Altogether, this work reveals the promising NL optical properties of Weyl semimetal thin films, which outperform bulk crystals of the same material, laying the grounds for nanoscale applications, enabled by top‐down nanostructuring, such as light‐harvesting, on‐chip frequency conversion, and all‐optical processing.

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Section: Resultsmentioning

confidence: 99%

Ultrafast Sub‐100 fs All‐Optical Modulation and Efficient Third‐Harmonic Generation in Weyl Semimetal Niobium Phosphide Thin Films

et al. 2022

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“…These results will be interesting for the investigation of the role of electronic decoherence, which is crucial for petahertz light-field information technology. In addition, the concept of light-field driven electrons has recently found attraction to investigate topological effects in gapped materials such as TMDCs using circular polarized driving pulses [57][58][59], which might become particularly interesting for Coulomb engineering of band gap materials [60].…”

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confidence: 99%

Sub-cycle temporal evolution of light-induced electron dynamics in hexagonal 2D materials

et al. 2020

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Two-dimensional materials with hexagonal symmetry such as graphene and transition metal dichalcogenides are unique materials to study light-field-controlled electron dynamics inside of a solid. Around the K-point, the dispersion relation represents an ideal system to study intricately coupled intraband motion and interband (Landau-Zener) transitions driven by the optical field of phase-controlled few-cycle laser pulses. Based on the coupled nature of the intraband and interband processes, we have recently observed in graphene repeated coherent Landau-Zener transitions between valence and conduction band separated by around half an optical period of 1.3 fs (Higuchi et al Nature 550, 224 (2017)). Due to the low temporal symmetry of the applied laser pulse, a residual current density and a net electron polarization are formed. Here we show extended numerical data on the temporal evolution of the conduction band population of 2D materials with hexagonal symmetry during the light-matter interaction, yielding deep insights to attosecond-fast electron dynamics. In addition, we show that a residual ballistic current density is formed, which strongly increases when a band gap is introduced. Both, the sub-cycle electron dynamics and the resulting residual current are relevant for the fundamental understanding and future applications of strongly driven electrons in two-dimensional materials, including graphene or transition metal dichalcogenide monolayers.

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“…We have shown that the topological resonance can be observed as a large conduction band population in some regions in the reciprocal space for two dimensional topological materials, such as gapped graphene-like materials or TMDCs, when these materials are placed in a circularly polarized pulse [10,17]. The topological resonance can be also realized in 3D topological solids such as Weyl semimetals in the field of a circularly polarized pulse [18]. The topological resonance is determined by nontrivial properties of Berry connections and the accumulation of the topological phase depends on the sign of the corresponding Berry curvature.…”

Section: Introductionmentioning

confidence: 94%

Topological resonance in graphene-like materials

Magar¹,

Motlagh²,

Apalkov³

2022

J. Phys.: Condens. Matter

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In topological materials, interacting with short and strong optical pulses, electrons can accumulate a topological phase during the pulse. Such phase can compensate the dynamic phase resulting in topological resonance, which is visible as a large inter-band transfer of electron population. We study theoretically the topological resonance in materials of the gapped multilayer graphene type. We show that the resonance can be observed only in the systems with ﬁnite bandgap. For graphene monolayer the topological resonance can occur only in the ﬁeld of an elliptically polarized pulse, while for graphene systems with many layers the topological resonance can be also realized in a linearly polarized pulse.

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Weyl semimetals in ultrafast laser fields

Cited by 21 publications

References 30 publications

Ultrafast Sub‐100 fs All‐Optical Modulation and Efficient Third‐Harmonic Generation in Weyl Semimetal Niobium Phosphide Thin Films

Ultrafast Sub‐100 fs All‐Optical Modulation and Efficient Third‐Harmonic Generation in Weyl Semimetal Niobium Phosphide Thin Films

Sub-cycle temporal evolution of light-induced electron dynamics in hexagonal 2D materials

Topological resonance in graphene-like materials

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