Single-band square lattice Hubbard model from twisted bilayer C568

TL;DR

This paper proposes using twisted bilayer C$_{568}$ to realize a controllable square lattice Hubbard model, enabling exploration of correlated electron phenomena and high-temperature superconductivity.

Contribution

It introduces a new carbon allotrope-based platform for tunable Hubbard models with adjustable parameters and discusses its potential for studying high-temperature superconductivity.

Findings

Derived tight-binding models from first-principles calculations.

Identified tunable $t'/t$ ratio without external fields.

Analyzed effects of displacement field on hopping anisotropy.

Abstract

We propose twisted homobilayer of a carbon allotrope, C$_{568}$, to be a promising platform to realize controllable square lattice single-band extended Hubbard model. This setup has the advantage of a widely tunable $t'/t$ ratio without adding external fields, and the intermediate temperature $t\ll T\ll U$ regime can be easily achieved. We first analyze the continuum model obtained from symmetry analysis and first-principle calculations, and calculate the band structures. Subsequently, we derive the corresponding tight-binding models and fit the hopping parameters as well as the Coulomb interactions. When displacement field is applied, anisotropic nearest neighbor hoppings can further be achieved. If successfully fabricated, the device could be an important stepping stone towards understanding high-temperature superconductivity.