High-harmonic Generation Spectroscopy in van der Waals Materials: Accessing Bloch Wavefunctions and Their Scattering Processes

High-harmonic generation (HHG) — an extreme nonlinear response to strong light fields — has emerged as a promising tool for probing femtosecond-to-attosecond electron dynamics in crystalline solids. This special topic article presents a perspective on how HHG spectroscopy has been applied to investigate microscopic electronic properties and carrier dynamics in van der Waals materials. Using examples of black phosphorus and transition-metal dichalcogenides, we discuss how HHG responses, depending on both driving-field conditions and material properties, can provide insight into microscopic physical quantities such as transition dipole moments, interband Berry phases, and ultrafast dynamics associated with scattering. These studies highlight the potential of HHG spectroscopy as a bridge between attosecond science and condensed matter physics, and its development is anticipated to be a strategic means for optical field control of carriers in solids.