How far in mean distance can electrons reasonably travel via ballistic conduction according to the current model and what is the current mean or average distance or length record for ballistic conduction in different materials? For instance the normal maximum average distance for graphene ribbons is different from that of carbon nanotubes.
The highest definitive value I could find was about 28 micrometers in graphene coated in hexagonal boron nitride below 200 Kelvin, see: https://pubs.acs.org/doi/abs/10.1021/acs.nanolett.5b04840 This study is from 2016 and I have not read of a higher value being achieved since then.
Another article involving multilayer nanotubes seems to indicate that over 100 micrometers is possible but doesn't seem very conclusive and came out in 2002 before more recent research that seems to always achieve much shorter values, see: https://pubs.acs.org/doi/10.1021/jp021271u "These discrepancies are not subtle but vast. Although the resistances per unit length of lithographically contacted nanotubes are found to be ρ =10 kΩ/μm,14 we show here that ρ < 100 Ω/μm for our freely suspended MWNTs, which implies mean free paths of the order of 100 μm (rather than at most a few hundred nm)."
Edited to account for statistical weirdness with maximum ballistic conduction distance as this question interested in the highest achieved average distance in a material and not a single electron randomly traveling farther than normal for a material in its environment.
