Speaker
Description
The ultrafast acceleration of electrons in solids by atomically strong light fields forms the basis of lightwave electronics [1,2]. When the field exceeds the adiabatic regime, non-adiabatic Landau–Zener–Majorana (LZM) tunnelling drives interband transitions at optical clock rates [3,4]. Graphene, with its Dirac-like dispersion and high damage threshold, is an ideal platform to study these effects, yet their direct observation remains challenging due to the need of both attosecond temporal resolution and full momentum-space access.
Here, we introduce subcycle band-structure videography across the entire first Brillouin zone, enabling direct tracking of lightwave-driven carrier dynamics with attosecond precision. Using intense few-cycle mid-infrared fields, we resolve the interplay of inter- and intraband processes in graphene. Coherent intraband acceleration and periodic LZM tunnelling induce characteristic modulations of the electron distribution in momentum space at the fundamental and second-harmonic frequencies of the driving field. At later times, carrier redistribution and thermalization indicate the gradual loss of coherence, marking the transition from single-particle to scattering-dominated many-body dynamics [5]. Our photoemission-based approach provides the first direct visualization of strongly driven electrons in full two-dimensional momentum space. It reveals how field-driven acceleration and interband coupling govern Dirac fermion motion and identifies scattering as the key limit to coherent evolution. These results uncover the microscopic dynamics of LZM tunnelling and mark a step toward coherent lightwave control in quantum materials and future petahertz electronics [1,2].
[1] Borsch et al., Nat. Rev. Mater. 8, 668 (2023).
[2] Ossiander et al., Nat. Commun. 13, 1620 (2022).
[3] Higuchi et al., Nature 550, 224 (2017).
[4] Boolakee et al., Nature 605, 251 (2022).
[5] Eggers et al., arXiv preprint arXiv:2602.12844 (2026).