The attoscience of strong-field-driven solids

The ultrafast dynamics of electrons in solid-state systems have garnered considerable attention recently, driven by technological advancements in the generation of short laser pulses from femtosecond down to attosecond durations. Techniques such as high-order harmonic generation (HHG) and attosecond transient absorption and reflection spectroscopy (ATAS and ATRS) provide valuable insights into sub-cycle dynamics, rendering the interaction of solids with intense laser fields a pivotal area of research. However, discrepancies in the explanation of the underlying mechanisms remain, requiring further analysis. This Perspective focuses on the relationship between the above techniques, highlighting their efficacy in probing charge dynamics induced by intense laser pulses in solid-state systems. We emphasize the importance of unified theoretical frameworks to advance our understanding of the strong-field attoscience of solids, while recognizing points of disparity between theoretical descriptions and experimental findings. By drawing attention to the complementary nature of HHG and both ATAS and ATRS, and by illustrating the key applications enabled by them, this Perspective aims to motivate stronger collaborations and concerted efforts to bridge the existing gaps between theory and experiment and propel the field forward. This Perspective explores attosecond physics in solids, focussing on high harmonic generation and attosecond transient absorption and reflection spectroscopy. Combining physical realizations and theoretical concepts is a challenge for future progress.