High-harmonic generation from spin-polarised defects in solids

The generation of high-order harmonics in gases enabled to probe the attosecond electron dynamics in atoms and molecules with unprecedented resolution.Extending these techniques to solids,which were originally developed for atomic and molecular gases,requires a fundamental understanding of the physics that has been partially addressed theoretically.Here,we employ timedependent density-functional theory to investigate how the electron dynamics resulting in high-harmonic emission in monolayer hexagonal boron nitride is affected by the presence of vacancies.We show how these realistic spin-polarised defects modify the harmonic emission and demonstrate that important differences exist between harmonics from a pristine solid and a defected solid.In particular,we found that the different spin channels are affected differently by the presence of the spin-polarised point defect.Moreover,the localisation of the wavefunction,the geometry of the defect,and the electron–electron interaction are all crucial ingredients to describe high-harmonic generation in defected solids.