G. M. Gusev

In a thin semiconductor channel, electrons behave not like lone runners but like a crowd at rush hour. They constantly bump into each other, and these collisions determine how easily heat and electric current pass through the material.

A ring-shaped channel of gallium arsenide is like a round pool with no rim: electrons flow in through the inner bank and out through the outer one. In an ultraclean material, they collide with each other more often than with lattice defects, and they begin to behave like a fluid.