Optical Distinctions Between Weyl Semimetal TaAs and Dirac Semimetal Na3Bi: An Ab Initio Investigation

Dadsetani, Mehrdad; Ebrahimian, Ali

doi:10.1007/s11664-016-4766-0

Cited by 24 publications

(20 citation statements)

References 52 publications

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“…This indicates that, with the decrease in incident photon energy, the electron transition process from the valence band to the conduction band occurs closer to the Weyl nodes, reducing the absorption. The normalized wavelength‐dependent absorptance agrees well with the theoretical calculation of the imaginary parts of the dielectric tensor for TaAs . Based on the calibration with a 1030 nm laser, the absorption coefficient α varied from 8.05 × 10 5 to 8.91 × 10 4 cm −1 with the corresponding penetration depth from 25 to 224 nm in the case of the wavelength ranging from 400 nm to 14 µm.…”

supporting

confidence: 75%

“…We considered that the increase in photon amount with the decreasing incident photon energy may be responsible for this phenomenon. In addition, the incident photons with lower energy (at wavelengths of 9.54 and 10.29 µm) can specifically excite electrons from the lower part of Weyl cone to the upper part, where exhibits a linear energy dispersion relation in all three momentum directions as the momentum moving away from the Weyl cones, resulting in significant enhancement of the efficiency of the photocurrent, as shown in the inset of Figure b.…”

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confidence: 99%

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A Wide‐Range Photosensitive Weyl Semimetal Single Crystal—TaAs

Chi

Xie

et al. 2018

Advanced Materials

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Mid- and even long-infrared photodetection is highly desired for various modern optoelectronic devices, and photodetectors that operate at room temperature (RT) remain challenging and are being extensively sought. Recently, the Weyl semimetal has attracted much interest, and its Lorentz invariance can be broken to have tilted chiral Weyl cones around the Fermi level, which indicates that the photocurrent can be generated by the incident photons at arbitrarily long wavelengths. Furthermore, the atypical linear dispersion bands in Weyl cones result in high carrier mobility and quadratic energy dependence of the density of states, which can enhance the efficiency of the photocurrent and suppress thermal carriers, in addition to its favorable large absorption coefficient. In this study, a Weyl semimetal TaAs photodetecting prototype is reported, which operates at RT with an outstanding response that ranges from the visible to the long-infrared range. This study indicates that the Weyl semimetal TaAs should boost the development of modern optoelectronics and photonics.

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confidence: 75%

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confidence: 99%

A Wide‐Range Photosensitive Weyl Semimetal Single Crystal—TaAs

Chi

Xie

et al. 2018

Advanced Materials

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“…Among all the 12 pairs of Weyl points therein, 8 pairs well sep-arated in momentum space off the k z = 0 plane are found to locate at the chemical potential while others lie rather lower, possibly leading to only 8 pairs determining the low-energy physics. We thus set N = 8 and take the typical values of Fermi velocities and relative permittivity [39,58] As a preliminary, let us first turn on an external magnetic field B = Bẑ for a general Weyl Hamiltonian i i k i σ i , in which i = ±1 and we assume the velocity equal to unity for simplicity. To solve this, we resort to the commutation relation between gauge invari-…”

Section: (B)mentioning

confidence: 99%

“…Among all the 12 pairs of Weyl points therein, 8 pairs well sep-5 arated in momentum space off the k z = 0 plane are found to locate at the chemical potential while others lie rather lower, possibly leading to only 8 pairs determining the low-energy physics. We thus set N = 8 and take the typical values of Fermi velocities and relative permittivity [39,58], v R = 2 × 10 5 m/s, v L = 1 × 10 5 m/s, ε r = 10 and hence v g = 0.35×10 5 m/s, and get η N = 1.83. Experimentally, to observe this, one should keep the temperature or frequency lower than the cyclotron gap to assure the dominance of the 1D channels.…”

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confidence: 99%

Tomonaga-Luttinger liquid and localization in Weyl semimetals

Zhang

Nagaosa

2017

Phys. Rev. B

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We study both noncentrosymmetric and time-reversal breaking Weyl semimetal systems under a strong magnetic field with the Coulomb interaction. The three-dimensional bulk system is reduced to many mutually interacting quasi-one-dimensional wires. Each strongly correlated wire can be approached within the Tomonaga-Luttinger liquid formalism. Including impurity scatterings, we inspect the localization effect and the temperature dependence of the electrical resistivity. The effect of a large number of Weyl points in real materials is also discussed.Introduction.-The realization of linear band crossings in three dimensions (3D) in the Weyl semimetals are sparking keen interests [1]. This lends credence to the concept of Weyl fermion [2] in the context of variou condensed matter systems [3,4]. In principle, any solid-state realization should bear time-reversal symmetry breaking (TRB) and/or inversion symmetry breaking (IB) [5][6][7][8][9] so as to lift the Kramers degeneracy and to generate nonzero Berry curvatures. The Weyl point is interesting as a 3D counterpart of the two-dimensional (2D) Dirac physics [10], which means topologically protected monopoles of the momentum-space Berry phase [11]. Among others, the chiral magnetic effect [12] as a result of the chiral anomaly [13][14][15][16] is observed as negative magnetoresistance in Dirac/Weyl semimetals [17,18] once the chiral imbalance of chemical potential is generated by parallel electric and magnetic fields.The intriguing facet of the magnetotransport in Dirac/Weyl semimetals mainly comes from the the unique Landau level formation dissimilar to that of quadratic electronic bands, where the lowest Landau level, a linearly dispersed chiral mode along the direction of the magnetic field, is well separated from the higher levels by a cyclotron gap ∝ √ B, whose 2D variant has been vastly explored in graphene [19]. A further stage is when the (ultra) quantum limit is achieved[20], enabling the lowest Landau level to play a major role in shaping the low-energy physics. In this limit, the magnetic length l B = 1/ √ eB (setting = 1) becomes shorter than the Fermi wavelength since the quantized orbit of electrons shrinks with an increasing B and the lowest Landau level possesses the majority of population [21]. Remarkably, it implies a field-induced dimensional reduction [22] that will strongly enhance correlations hence the advent of the (quasi-) 1D system without electron quasiparticle excitations. This connects to the long-lasting search or application of the Tomonaga-Luttinger liquid (TLL) physics [23], including semiconductor quantum wires [24,25], singlewalled carbon nanotubes [26,27], edge states in fractional quantum Hall states [28,29] and 2D topological insulators [30,31], and so on.Because of the large cyclotron gap, it is expected and confirmed that the Dirac/Weyl semimetals can be driven to the quantum limit at lower magnetic fields than semiconductors [20]. Due to the instability from electron correlations, one possibility is the gap-opening or dynamical m...

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“…small Dirac cone velocity and small dielectric constant), (ii) [32], and ε = 36 [58]. For the TaAs family, v ≈ 2.5 × 10 5 m/s [59], Λ ≈ 200 meV [9,59], and ε = 10 [60]. For hypothetical 3D DMs the cutoff energy scale 1 eV is assumed.…”

Section: Estimates Of Critical Temperature and Excitonic Gapmentioning

confidence: 99%

Excitonic instability in optically pumped three-dimensional Dirac materials

Pertsova

Balatsky

2018

Phys. Rev. B

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Recently it was suggested that transient excitonic instability can be realized in optically-pumped two-dimensional (2D) Dirac materials (DMs), such as graphene and topological insulator surface states. Here we discuss the possibility of achieving a transient excitonic condensate in opticallypumped three-dimensional (3D) DMs, such as Dirac and Weyl semimetals, described by nonequilibrium chemical potentials for photoexcited electrons and holes. Similar to the equilibrium case with long-range interactions, we find that for pumped 3D DMs with screened Coulomb potential two possible excitonic phases exist, an excitonic insulator phase and the charge density wave phase originating from intranodal and internodal interactions, respectively. In the pumped case, the critical coupling for excitonic instability vanishes; therefore, the two phases coexist for arbitrarily weak coupling strengths. The excitonic gap in the charge density wave phase is always the largest one. The competition between screening effects and the increase of the density of states with optical pumping results in a reach phase diagram for the transient excitonic condensate. Based on the static theory of screening, we find that under certain conditions for the value of the dimensionless coupling constant screening in 3D DMs can be weaker than in 2D DMs. Furthermore, we identify the signatures of the transient excitonic condensate that could be probed by scanning tunneling spectroscopy, photoemission and optical conductivity measurements. Finally, we provide estimates of critical temperatures and excitonic gaps for existing and hypothetical 3D DMs.

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Optical Distinctions Between Weyl Semimetal TaAs and Dirac Semimetal Na3Bi: An Ab Initio Investigation

Cited by 24 publications

References 52 publications

A Wide‐Range Photosensitive Weyl Semimetal Single Crystal—TaAs

A Wide‐Range Photosensitive Weyl Semimetal Single Crystal—TaAs

Tomonaga-Luttinger liquid and localization in Weyl semimetals

Excitonic instability in optically pumped three-dimensional Dirac materials

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