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

TL;DR

This paper proposes a highly efficient quantum Otto engine based on twisted bilayer graphene, exploiting flat bands at magic angles to optimize work extraction and efficiency.

Contribution

It introduces a novel quantum Otto engine design utilizing twisted bilayer graphene's flat bands at magic angles, with efficiency analysis across different twist angles.

Findings

Efficiency peaks at the magic angle.

Flat bands enhance work extraction.

Efficiency varies smoothly with twist angle.

Abstract

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 work, we design a highly efficient quantum Otto engine using a twisted bilayer graphene sample. Flat bands, which occur at magic angles, make the prospect of extracting useful work from our Otto engine lucrative. We use an eight-band continuum model of twisted bilayer graphene to compute efficiencies and work outputs for magic and non-magic 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.