Strain-controlled high harmonic generation with Dirac fermions in silicene

TL;DR

This study demonstrates that mechanical strain can controllably enhance high harmonic generation in silicene by modulating its electronic structure, providing new opportunities for nanoscale optoelectronic devices and understanding Dirac fermion nonlinear dynamics.

Contribution

It reveals how mechanical strain tuning of silicene's electronic structure enhances HHG, a novel approach for controlling nonlinear optical responses in 2D Dirac materials.

Findings

HHG intensity can be increased by an order of magnitude through strain.

Dirac cones in silicene are preserved under biaxial and uniaxial strains.

Strain tuning offers a controllable method to modulate nonlinear optical properties.

Abstract

Two-dimensional (2D) materials with zero band gap exhibit remarkable electronic properties with wide tunability. High harmonic generation (HHG) in such materials offers unique platforms to develop novel optoelectronic devices at nanoscale, as well as to investigate strong-field and ultrafast nonlinear behaviour of massless Dirac fermions. However, control of HHG by modulating electronic structure of materials remains largerly unexplored to date. Here we report controllable HHG by tuning the electronic structures via mechanical engineering. Using an \textit{ab initio} approach based on time-dependent density-functional theory (TDDFT), we show that the HHG process is sensitive to the modulation of band structures of monolayer silicene while preserving the Dirac cones under biaxial and uniaxial strains, which can lead to significant enhancement of harmonic intensity up to an order of magnitude. With the additional advantage of silicene in compatibility and integration into the current silicon-based electronic industry, this study may open a new avenue to develop efficient solid-state optoelectronic nano-devices, and provide a valuable tool to understand the strong-field and mechanically induced ultrafast nonlinear response of Dirac carriers in 2D materials.