Strong tunable photomixing in semi-Dirac materials in the terahertz regime

Huang, Sunchao; Tran, My Hanh; Zuber, Jack; Wang, Qian; Zhu, Yiming; Zhang, Chaofeng

doi:10.1364/josab.36.000200

Cited by 7 publications

(3 citation statements)

References 21 publications

(18 reference statements)

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“…In the low-energy limit, the electrons in these exotic materials obey relativistic, Diraclike Hamiltonians. Their pseudo-massless particle behavior confers these materials unique optical properties such as high electromagnetic field confinement [1][2][3][4] and strong optical nonlinearity, [5][6][7][8][9][10][11][12][13][14][15][16] making them desirable for uses like tabletop generation of high-brightness coherent radiation spanning from the x-ray to the terahertz regimes through mechanisms such as free-electron-graphene plasmon scattering, [17,18] highharmonic generation, [19][20][21][22] and transition radiation, [23] and also as saturable absorbers for infrared ultrafast lasers. [24][25][26][27] Recently, a new class of quantum materials which behave like the bulk analogues of graphene have also attracted significant attention -3D Dirac semimetals (DSMs).…”

Section: Introductionmentioning

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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Section: Introductionmentioning

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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show abstract

“…The formation of the polaron (or even the trion) and the polariton have been realized in semiconductor heterostructure by using the technique of cavity coupling in the presence of exciton-electron interactions [22,23]. For semi-Dirac system, which has very interesting electronic and topological properties under irradiation [24,25,26], although its anisotropic dispersion, we can still approximate it as the one similar to the twodimensional electron gas when the carrier density is just slightly larger than the band gap (D ≫ µ ↑ − D > 0) and with small momentum. In the mean time, the chemical potential of the impurity can be treated as a negative unphysical parameter µ ↓ < −µ ↑ during the calculation of the polaron energy (i.e., the pole of the dressed Green's function).…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Electronic properties and polaronic dynamics of semi-Dirac system within Ladder approximation

2020

Phys. Scr.

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We investigate the electronic properties of the semi-Dirac system and its polaronic dynamics when coupled with a fermi bath with quadratic dispersion. The electronic anisotropic transport properties and the semiclassical dynamics of the semi-Dirac system are studied, including the density-of-states, conductivity, transport relaxation rate, specific heat, electrical current denity, and free energy. The attractive polaron formed as the semi-Dirac impurity dressed with the particle-hole excitations in a two-dimensional system are studied both analytically and numerically. The pair propagator, self-energy, spectral function are being detailly calculated and discussed. The method of medium T -matrix approximation (non-self-consistent), which equivalent to the partially dressed interaction vertex by summing over all ladder diagrams, is applied, and compared with some other methods (for many-body problem), like the leading-order 1/N expansion (GW approximation), Hartree-Fock theory, and the Nozieres-Schmitt-Rink theory. Since we foucs on the weak-coupling region, the mean-field approximation is also applicable. The polaron properties is related to the anisotropic effective masses of the semi-Dirac system. That's in contrast to the polarons formed in the surface of normal Dirac systems which has an isotropic dispersion, since the anisotropic dispersion of the semi-Dirac systems results in anisotropic effective mass and anisotropic charge carrier transport. Besides, the symmetry between electron and hole is also broken since the effective masses of the electron and hole are different, which are affected by the polaronic effect when the semi-Dirac material is deposited on a polar substrate, like hBN. The self-localization, short-range potential, and experimental methods as well as the possible formation of the bose polaron on the surface of semi-Dirac system are also discussed in the end. Our results are useful also for the investigation of two/three-dimensional bosonic polaron as well as the polarons in other solid state systems, like the magnetic matter or the topological systems. *

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Thermionic emission in nodal-ring semimetals

Chen

Huang

Duan

et al. 2020

Journal of Applied Physics

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We theoretically investigate the thermionic emission from nodal-ring semimetals. The thermionic emission is found to be anisotropic in the x- and y-directions. The anisotropic emission can be enhanced by increasing the radius of nodal-ring b. The main feature of nodal-ring semimetals not only results in anisotropic thermionic emission but also affects the value of thermionic emission current density (TECD). The TECD of the lower branch of the energy–momentum dispersion increases with b, while the TECD of the upper branch decreases with b. Unlike in conventional materials, the TECD in nodal-ring semimetals depends on Fermi energy that is similar to the situation in Dirac semimetals. The underlined reason is that Dirac semimetals and nodal-ring semimetals have a linear or a linear-like energy–momentum dispersion while conventional materials have a parabolic energy–momentum dispersion. The TECD of nodal-ring semimetals depends strongly on work function and temperature.

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Strong tunable photomixing in semi-Dirac materials in the terahertz regime

Cited by 7 publications

References 21 publications

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

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

Electronic properties and polaronic dynamics of semi-Dirac system within Ladder approximation

Thermionic emission in nodal-ring semimetals

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