Simulating twistronics without a twist

TL;DR

This paper proposes a method to emulate twisted bilayer graphene using ultracold atoms in optical lattices, creating synthetic layers and supercell structures to study flat bands and Dirac cones without physical twisting.

Contribution

It introduces a novel scheme to simulate twisted bilayer systems with ultracold atoms, avoiding the need for actual physical bilayers or twisting, enabling controlled studies of correlated electronic phenomena.

Findings

Synthetic bilayer lattice exhibits tunable flat bands.

Emergence of Dirac cones at specific supercell periodicities.

Perturbative analysis explains the spectral features.

Abstract

Rotational misalignment or twisting of two mono-layers of graphene strongly influences its electronic properties. Structurally, twisting leads to large periodic supercell structures, which in turn can support intriguing strongly correlated behaviour. Here, we propose a highly tunable scheme to synthetically emulate twisted bilayer systems with ultracold atoms trapped in an optical lattice. In our scheme, neither a physical bilayer nor twist is directly realized. Instead, two synthetic layers are produced exploiting coherently-coupled internal atomic states, and a supercell structure is generated \emph{via} a spatially-dependent Raman coupling. To illustrate this concept, we focus on a synthetic square bilayer lattice and show that it leads to tunable quasi-flatbands and Dirac cone spectra under certain magic supercell periodicities. The appearance of these features are explained using a perturbative analysis. Our proposal can be implemented using available state-of-the-art experimental techniques, and opens the route towards the controlled study of strongly-correlated flat band accompanied by hybridization physics akin to magic angle bilayer graphene in cold atom quantum simulators.