  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.
