Influence of vacancy defects in solid high-order harmonic generation

Abstract

The present work discusses the impact of vacancy defects in solid high-order harmonic generation. The total energy cut off of the high-order harmonic spectrum increases as a function of concentration of vacancy defect, and the total spectrum gradually turns into a single slanted spectrum without having an abrupt transition between primary and secondary plateaus. The spectral intensity of the below band-gap harmonics in a solid with vacancy defects is enhanced significantly in comparison to the harmonics in a pristine solid. The changes in the harmonic spectra are understood in terms of their effective band structures. The presence of vacancy defects breaks the translational symmetry of the unit cell locally. As a consequence of this, new defect states appear, which open additional paths for the electron dynamics. The ill-resolved electron trajectories in the Gabor profile confirm the interference of additional paths. Moreover, the single slanted high-order harmonic spectrum carries a unique signature of vacancy defects in comparison to the high-order harmonic spectrum corresponding to solids with defects such as underdoping or overdoping.

Effects of vacancies on high-order harmonic generation in a linear chain with band gap

“…However, in this case, the irregularity is induced by breaking the lattice periodicity by random shifts of ionic locations. Very recently, the appearance of ill-resolved electron trajectories in the Gabor profile of systems with vacancies were related to the interference of additional paths for the electron dynamics introduced by the defect states [49].…”

High-harmonic generation from spin-polarised defects in solids

“…There are various theoretical predictions for the HHG from doped semiconductors by using simple onedimensional model Hamiltonians. [38][39][40] In ref., 38 by using TDDFT, it is predicted that there is an enhancement of several orders of magnitude in the efficiency of HHG in a donor-doped semiconductor. Using an independent particle model, Huang et al contrastingly found that the efficiency of the second plateau from the doped semiconductor is enhanced.…”

High-Harmonic Generation from Monolayer and Bilayer Graphene

“…After a pioneering work of Ghimire et al 2 , HHG in solids has opened the door to study the electronic structure and its dynamics with the characteristic timescale in solids 1,3 . In recent years, HHG in solids has employed to explore several exciting processes such as band structure tomography [4][5][6] , probing the dynamics of the defects in solids 7,8 , the realisation of petahertz current in solids 9,10 , Bloch oscillations 11,12 are few to name. Moreover, HHG in solids offers an attractive all-solid-state compact optical device to obtain coherent and bright attosecond pulses in extreme ultraviolet energy regime 1,3,13 .…”