Graphene electron motion comes into view within a light cycle
A single peer-reviewed physics experiment tracked light-driven electron distributions across graphene’s entire first Brillouin zone, resolving changes within a light cycle. The measurements separated acceleration within energy bands from transitions between them and examined competing scattering processes. The method images energy and momentum distributions, offering a wider view of coherent electronic control rather than following individual electrons through real space.
Science··Evening
Electron distributions are resolved across the first Brillouin zone
A single peer-reviewed physics experiment imaged light-driven electron motion across graphene's entire first Brillouin zone, a fundamental region of momentum space used to describe a crystal's electronic structure. Attosecond-precision timing resolved changes within a light cycle. Earlier subcycle methods covered a narrower range of momenta. The new view showed how strong fields shift and distort carrier distributions near the zone boundary.[1]
Infrared driving meets ultraviolet snapshots
Researchers used a single graphene layer on a silicon carbide substrate. Its electrons were driven using mid-infrared pulses, and extreme-ultraviolet probe pulses emitted photoelectrons for a momentum microscope that measured flight times. The arrangement combined energy and momentum information. Comparing measurements with microscopic quantum calculations distinguished acceleration within an energy band from Landau–Zener–Majorana tunnelling between bands, a transition induced by rapidly changing fields.[1]
Strongly non-thermal electron distributions allowed competing scattering processes and their effects on coherent motion to be assessed. The images represent changing energy- and momentum-space populations, rather than camera pictures following individual electrons through real space. The immediate result is a wider experimental view of control in graphene. The method could also be applied in other quantum materials; an operating light-frequency processor was not demonstrated.[1]
