Optical conductivity of the type-II Weyl semimetal TaIrTe4

Abstract

TaIrTe 4 is an example of a candidate Weyl type-II semimetal with a minimal possible number of Weyl nodes. Four nodes are reported to exist in a single plane in k space. The existence of a conical dispersion linked to Weyl nodes has yet to be shown experimentally. Here, we use optical spectroscopy as a probe of the band structure on a low-energy scale. Studying optical conductivity allows us to probe intraband and interband transitions with zero momentum. In TaIrTe 4 , we observe a narrow Drude contribution and an interband conductivity that may be consistent with a tilted linear band dispersion up to 40 meV. The interband conductivity allows us to establish the effective parameters of the conical dispersion; effective velocity v = 1.1 × 10 4 m/s and tilt γ = 0.37. The transport data, Seebeck and Hall coefficients, are qualitatively consistent with conical features in the band structure. Quantitative disagreement may be linked to the multiband nature of TaIrTe 4 .

A Raman probe of phonons and electron–phonon interactions in the Weyl semimetal NbIrTe4

“…This removes both the ω 4 term and any dependence of the measurement from the Raman instrument and detector. By comparison with reflectivity measurements in the closely related materials TaIrTe 4 48 and WTe 2 49 we do not expect any large change in the dielectric response (real or imaginary parts) with laser excitation energy which might also impact the Raman measurements. The penetration depth is also substantially less than the nanoflake thickness.…”

Dynamical evolution of anisotropic response of type-II Weyl semimetal TaIrTe4 under ultrafast photoexcitation

“…3d for the pump wavelength at 2 μm. The value of complex optical conductivity ( σ ) of bulk TaIrTe 4 is taken to be (1.7 × 10 3 – i × 5.6 × 10 2 ) Ω −1 /cm according to the infrared spectroscopy experiment 27 . The absolute value Re ( σ xx ): Re ( σ yy ) at 4 μm can be larger according to previous polarization-dependent photocurrent measurement at different excitation wavelength 5 , but this does not affect the qualitative results that the response becomes more isotropic in presence of hot carriers.…”

Direct Light Orbital Angular Momentum Detection in Mid‐Infrared Based on the Type‐II Weyl Semimetal TaIrTe4

“…The typical thickness of TaIrTe 4 flakes used for device fabrication is between 100 and 200 nm, which is close to the penetration depth (≈140 nm) of TaIrTe 4 at 4 µm. [ 19 ] Figure 1c shows the schematic of the OPGE measurement on a U‐shaped electrode device. When the OAM order of light is switched from +| m | to −| m |, the radial current from the OPGE effect switches its sign, while its amplitude should be proportional to the OAM order ( m ) according to Equation (S11), Supporting Information.…”