Magic angle twisted bilayer graphene as a highly efficient quantum Otto engine

At a discrete set of magic angles, twisted bilayer graphene has been shown to host extraordinarily flat bands, correlated insulating states, unconventional superconductivity, and distinct Landau level degeneracies. In this paper, we design a highly efficient quantum Otto engine using a twisted bilayer graphene sample. Flat electronic bands at magic angles make the prospect of extracting work from our Otto engine lucrative because exploiting correlated phenomena may lead to nanoscale devices operating at considerably larger efficiencies. We use an eight-band continuum model of twisted bilayer graphene to compute efficiencies and work outputs for magic and nonmagic angle twists and compare the results with an $AB$ stacked bilayer and a monolayer. It is observed that the efficiency varies smoothly with the twist angle, and the maximum is attained at the magic angle.