Research ArticlePHYSICS

Atomic-like high-harmonic generation from two-dimensional materials

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Science Advances  16 Feb 2018:
Vol. 4, no. 2, eaao5207
DOI: 10.1126/sciadv.aao5207
  • Fig. 1 HHG from monolayer hBN.

    (A) HHG spectrum for an out-of-plane driving electric field with a wavelength of λ = 1600 nm, an intensity of I0 = 1014 W cm–2 in vacuum, and a pulse duration of 15-fs full width at half maximum (FWHM). The red line indicates the energy cutoff predicted by the three-step model (Ec = Ew + 3.17 Up). (B) Time-frequency analysis of the harmonic emission. We used a window of 0.25 fs to compute the Gabor transform. The vector potential of the laser is shown in the inset. Red dashed lines indicate the half-cycle energy cutoffs (see main text).

  • Fig. 2

    Evolution of the induced electronic density, averaged in the plane of the monolayer and taken along the out-of-plane direction (z direction), for the same laser parameters as in Fig. 1.

  • Fig. 3 Anisotropy effect on the HHG from monolayer hBN.

    (A) Time-dependent electronic current along the out-of-plane direction, computed within the LDA (red curve) and within the LDA, but by freezing the Coulomb and exchange-correlation terms to their ground-state value (independent-particle approximation; blue dashed curve). (B) Corresponding HHG spectra. The spectrum corresponding to the frozen LDA calculation or independent-particle approximation (blue dashed curve) is divided by a factor of 10 to ease the comparison. The laser parameters are the same as in Fig. 1.

  • Fig. 4 Polarization of the induced density by the driving laser field.

    The evolution of the in-plane–averaged induced electronic density, taken along the out-of-plane direction (z direction), is responsible for the local-field effects screening the external perturbation. The inset shows the evolution of the induced density at the end and after the end of the laser pulse. The laser parameters are the same as in Fig. 1.

  • Fig. 5 Calculated wavelength scaling of the harmonic yield.

    The harmonic yield was obtained from the TDDFT simulations (black point), integrated from 15 to 35 eV, as a function of the wavelength, compared to the fitted λ− 4.73 power law.

Supplementary Materials

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. HHG spectra of monolayer hBN for various wavelengths.
    • fig. S2. In-plane HHG spectra of monolayer hBN.

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