Question: why do electrons travel through a graphine sheet as if they have no mass

Edward Bovill answered on 12 Mar 2013:

Graphene is a sheet of carbon atoms only a single atom thick. The key to the behaviour of the electrons is graphene’s structure. This is most easily visualized as a hexagonal pattern, or atomic-scale chicken wire with carbon atoms at the points where the wires join.

This very specific hexagonal arrangement of carbon atoms in a sheet only one atom thick leads to some very odd electron behaviour. Due to a very strong interaction between the electrons and this hexagonal pattern, the electrons all move as one big mass, instead of individually, at only 1/300th the speed of light (which is incredibly fast for electrons in solid matter).

This is where things get very complicated: as the electrons move so fast and all in one big group, they are treated as relativistic particles and are said to have no ‘rest mass’, which is a phrase that comes from Einstein’s theory of relativity. According to relativity, as you increase your speed you also increase your mass; ‘rest mass’ is the mass an object or particle has when it isn’t moving. The actual details of what’s happening to the electrons is lost in some very complicated mathematics from quantum mechanical theory.

If you want to understand this in more detail I’d suggest a degree in Physics 🙂