Enhanced higher harmonic generation from nodal topology

Lee, Ching Hua; Yap, Han Hoe; Tai, Tommy; Xu, Gang; Zhang, Xiao; Gong, Jiangbin

doi:10.48550/arxiv.1906.11806

Cited by 1 publication

(1 citation statement)

References 57 publications

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“…We found that the optical conductivity exhibits strong anisotropy with the universal scaling law, Λ i j = (v i /v j ) 2 , independent of temperature, Fermi level, and scattering effects, and is broadly applicable to the sub-THZ to at least 50 THz frequency window. Recently, the optical properties of topological semimetals with nodal topology beyond Dirac semimetal, such as Weyl semimetal [74] and nodal loop semimetal, [75][76][77][78] have been extensively studied. We expect this ever-expanding family of topological semimetals, [79] in which the optical and electronic properties are highly anisotropic along different crystal directions, to continually offer interesting platforms for the uncovering of exotic anisotropic optics and optoelectronic phenomena critical for the design of next-generation novel devices.…”

Section: Discussionmentioning

confidence: 99%

Broadband strong optical dichroism in topological Dirac semimetals with Fermi velocity anisotropy*

Lim¹,

Ooi²,

Zhang³

et al. 2020

Chinese Phys. B

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Prototypical three-dimensional (3D) topological Dirac semimetals (DSMs), such as Cd3As2 and Na3Bi, contain electrons that obey a linear momentum–energy dispersion with different Fermi velocities along the three orthogonal momentum dimensions. Despite being extensively studied in recent years, the inherent Fermi velocity anisotropy has often been neglected in the theoretical and numerical studies of 3D DSMs. Although this omission does not qualitatively alter the physics of light-driven massless quasiparticles in 3D DSMs, it does quantitatively change the optical coefficients which can lead to nontrivial implications in terms of nanophotonics and plasmonics applications. Here we study the linear optical response of 3D DSMs for general Fermi velocity values along each direction. Although the signature conductivity-frequency scaling, σ(ω) ∝ ω, of 3D Dirac fermion is well-protected from the Fermi velocity anisotropy, the linear optical response exhibits strong linear dichroism as captured by the universal extinction ratio scaling law, Λij = (vi /vj )2 (where i ≠ j denotes the three spatial coordinates x,y,z, and vi is the i-direction Fermi velocity), which is independent of frequency, temperature, doping, and carrier scattering lifetime. For Cd3As2 and Na3Bi3, an exceptionally strong extinction ratio larger than 15 and covering a broad terahertz window is revealed. Our findings shed new light on the role of Fermi velocity anisotropy in the optical response of Dirac semimetals and open up novel polarization-sensitive functionalities, such as photodetection and light modulation.

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