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Edge-state-induced correlation effects in two-color pump-probe high-order harmonic generation

Simon Vendelbo Bylling Jensen, Hossein Iravani, and Lars Bojer Madsen
Phys. Rev. A 103, 053121 – Published 26 May 2021
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  • INTRODUCTION
  • THEORETICAL MODEL AND METHODS
  • RESULTS AND DISCUSSION
  • CONCLUSIONS
  • ACKNOWLEDGMENTS
    • References

    Abstract

    For a finite-sized generic nanostructured band gap material, it is shown that significant laser-induced correlation effects can be introduced by a two-color pump-probe scheme where edge states are resonantly pre-excited by the pump before the probe arrives and drives the generation of high-order harmonics. Compared with the response of a bulk sample, we demonstrate an increase in the efficiency of the generated high-harmonic signal over a wide range of frequencies by harnessing the power of these ultrafast many-electron dynamics.

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    • Received 20 October 2020
    • Revised 19 January 2021
    • Accepted 5 May 2021

    DOI:https://doi.org/10.1103/PhysRevA.103.053121

    ©2021 American Physical Society

    Physics Subject Headings (PhySH)

    1. Research Areas
    Atomic & molecular processes in external fieldsEdge statesElectrical propertiesHigh-order harmonic generationMultiphoton or tunneling ionization & excitationStrong electromagnetic field effects
    1. Physical Systems
    1-dimensional systems
    1. Techniques
    Density functional theorySchroedinger equation
    Atomic, Molecular & OpticalCondensed Matter, Materials & Applied PhysicsNonlinear Dynamics

    Authors & Affiliations

    Simon Vendelbo Bylling Jensen1, Hossein Iravani2, and Lars Bojer Madsen1

    • 1Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
    • 2Department of Chemistry, Tarbiat Modares University, P.O. Box 14115-175, Tehran, Iran

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    Issue

    Vol. 103, Iss. 5 — May 2021

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    Images

    • Figure 1
      Figure 1

      (a) Band structure with the highest energy valence band (VB) and the lowest energy conduction band (CB). The edge states (ESs) are indicated below the CB by the horizontal line at ≈−0.18. The free-space (FS) dispersion is visible. Arrows denote central photon energies: the smallest red arrows depicting the 11ωd multiphoton transition, 1. illustrating the pre-excitation pulse when resonant with the ES, and 2. the pre-excitation pulse off-resonant with the ES. (b) The norm-squared wave function in real space of the ES below CB for an N=80 system. (c) Two-color pump-probe pulse sequence with the ultraviolet (UV) pre-excitation pump and the infrared (IR) driving laser pulses in units of the period of the IR laser Td and with each pulse normalized individually. The pulses drive the transitions in (a), see text for parameters.

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    • Figure 2
      Figure 2

      High-harmonic generation (HHG) spectra (a) for a finite-sized system (N=80) and (b) bulk system for two-color pump-probe and infrared (IR)-only (nd=15-cycle IR pulse with ωd=0.023 and F0,d=0.00552) references in correlated and independent-electron descriptions. (c) Ratio between the pump-probe signal for correlated and independent electrons for N=80 and the bulk system. The 153-cycle ultraviolet (UV) pump with ωp=0.235, F0,p=0.0005, and resonant with the edge states (ESs) [see Figs. 1 and 1(c)] was at a time τ=26Td earlier than the IR probe.

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    • Figure 3
      Figure 3

      As Fig. 2, but for ωp=0.455575, off resonant with the edge states (ESs) [see Fig. 1].

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    • Figure 4
      Figure 4

      (a) High-harmonic generation (HHG) spectra of a finite (N=80) system as a function of time-delay between pre-excitation by an np=153-cycle ultraviolet (UV) pulse with ωp=0.235 and F0,p=0.0005 and a nd=2-cycle infrared (IR) pulse with ωd=0.023 and F0,d=0.00552 driving pulse, applying correlated dynamical propagation. (b) The density fluctuations n(x,t)−n(x,0) of the system applying the correlated dynamical method given as a function of time, with parameters of (a) but with no driving field. (c) HHG spectra at certain τ from (a) compared with spectra from calculations in the same setting but with an independent-electron approach.

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