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The magnetic-field dependence of optical reflectivity [$R(omega)$] and optical conductivity [$sigma(omega)$] spectra of the ideal type-I Weyl semimetal TaAs has been investigated at the temperature of 10 K in the terahertz (THz) and infrared (IR) regions. The obtained $sigma(omega)$ spectrum in the THz region of $hbaromegaleq15$ meV is strongly affected by the applied magnetic field ($B$): The Drude spectral weight is rapidly suppressed and an energy gap originating from the optical transition in the lowest Landau levels appears with a gap size that increases in proportion to $sqrt{B}$, which suggests linear band dispersions. The obtained THz $sigma(omega)$ spectra could be scaled not only in the energy scale by $sqrt{B}$ but also in the intensity by $1/sqrt{B}$ as predicted theoretically. In the IR region for $hbaromegageq17$ meV, on the other hand, the observed $R(omega)$ peaks originating from the optical transitions in higher Landau levels are proportional to linear-$B$ suggesting parabolic bands. The different band dispersions originate from the crossover from the Dirac to the free-electron bands.
We investigate polarization-dependent ultrafast photocurrents in the Weyl semimetal TaAs using terahertz (THz) emission spectroscopy. Our results reveal that highly directional, transient photocurrents are generated along the non-centrosymmetric c-ax
It is shown that the Weyl semimetal TaAs can have a significant polar vector contribution to its optical activity. This is quantified by ab initio calculations of the resonant x-ray diffraction at the Ta L1 edge. For the Bragg vector (400), this pola
Weyl semimetals are a class of materials that can be regarded as three-dimensional analogs of graphene breaking time reversal or inversion symmetry. Electrons in a Weyl semimetal behave as Weyl fermions, which have many exotic properties, such as chi
While all media can exhibit first-order conductivity describing current linearly proportional to electric field, $E$, the second-order conductivity, $sigma^{(2)}$ , relating current to $E^2$, is nonzero only when inversion symmetry is broken. Second
Symmetry plays a central role in conventional and topological phases of matter, making the ability to optically drive symmetry change a critical step in developing future technologies that rely on such control. Topological materials, like the newly d