Tunable bandgaps and flat bands in twisted bilayer biphenylene carbon

TL;DR

This study explores how twisting bilayer biphenylene carbon alters its electronic properties, revealing tunable bandgaps, flat bands at various angles, and potential for advanced optoelectronic applications.

Contribution

It demonstrates the existence of twist-angle-dependent electronic phase transitions and flat bands in twisted bilayer biphenylene carbon, expanding understanding beyond twisted bilayer graphene.

Findings

Twist induces a semiconductor to metal phase transition.

Band gap in BPC can be tuned from 0 to 120 meV.

Flat bands appear at specific large angles, not limited to magic angles.

Abstract

Owing to the interaction between the layers, the twisted bilayer two-dimensional materials exhibit numerous unique optical and electronic properties different from the monolayer counterpart, and have attracted tremendous interests in current physical research community. By means of first-principles and tight-binding model calculations, the electronic properties of twisted bilayer biphenylene carbon are systematically investigated in this paper. The results indicate that the effect of twist will not only leads to a phase transition from semiconductor to metal, but also an adjustable band gap in BPC (0 meV to 120 meV depending on the twist angle). Moreover, unlike the twisted bilayer graphene (TBG), the flat bands in twisted BPC are no longer restricted by "magic angles", i.e., abnormal flat bands could be appeared as well at several specific large angles in addition to the small angles. The charge density of these flat bands possesses different local modes, indicating them might be derived from different stacked modes and host different properties. The exotic physical properties presented in this work foreshow twisted BPC a promising material for the application of terahertz and infrared photodetectors and the exploration of strong correlation.