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High-Harmonic generation from spin-polarised defects in solids

Generation of high-order harmonics in gases enabled to probe the attosecond electron dynamics in atoms and molecules with unprecedented resolution. Extending the techniques developed originally for atomic and molecular gases to solid state materials requires a fundamental understanding of the physics that has been partially addressed theoretically. Here we employ time-dependent 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 because of the presence of the spin-polarized point defect, and that localisation of the wavefunction, the geometry of the defect and the electron-electron interaction are all important ingredients to describe high-harmonic generation in defected-solids. We show that different vacancies lead to qualitatively different effects, thus opening the door to the high-harmonic imaging of spin-polarised defects in solids.