Incredible electron drift velocity in atomic thin layer of graphene?

Question

Free electrons in atomic thin layers of graphene behave more like photons (Bosons) than fermions reaching incredible drift velocities and mobility which reach speeds as reported by this article in the order of $700Km/s$ or more (see Abstract figure in above referenced article). These are incredible drift velocities relative to the sub-millimeter or less per second velocities in normal conductors.

This reminds me however of the drift velocity of electron Cooper Pairs in Type I superconductors where we have very similar values.

Are these two apparent different phenomena, quantum mechanisms, somehow correlated or similar leading to this increased electron mobility?

Or if not what exactly are the mechanics of atomic thin layer of graphene that results to this incredible mobility despite the fact that graphite (bulk form of graphene) is not the best conductor of electricity?

How is it possible graphene to achieve such speeds similar to superconductors but at room temperature!?

Would it not be more practical and feasible to consider graphene nanotube wires for power transmission instead of superconductors? (Current superconductors demand very low temperatures which are impractical for power transmission).

Additional Reference: article (speeds reported not for atomic thin layer but Ultra thin layer graphene semiconductors. Speed up to $200Km/s$ or more at room temperature, see fig.3).

Answer 1

I would say that superconductivity and the high mobility of graphene are completely unrelated.

From my understanding, the high mobility of graphene comes from two things. One is the intrinsic band structure. Graphene has a symmetry protected band crossing, which means that the low energy Hamiltonian is that of massless Dirac fermions, in contrast to a normal metal where you have a quadratic band dispersion. This leads to a very high Fermi velocity, which is essentially the slope of the Dirac cone in momentum space.

The second thing is that graphene is naturally a very clean system, with few extrinsic defects. This is related to the fact that it is only one atom thick and has very strong in plane bonds. This leads to a very long mean free path where the electrons can travel a long distance without scattering.

Interestingly enough, graphene does not have the highest mobility of two dimensional materials or heterostructures. Some of the highest mobilities are found in GaAs/GaAlAs heterostructures which can have mobility > 10^7 cm^2/Vs and are achieved through highly optimized and clean growth via molecular beam epitaxy. These high mobilities are what allowed us to observe interacting quantum phenomenon such as the fractional quantum hall effect in these systems.