Origami-controlled strain engineering of tunable flat bands and correlated states in folded graphene

TL;DR

This paper demonstrates a method to create and tune flat electronic bands in folded graphene through nano origami-controlled strain engineering, enabling the exploration of correlated quantum states.

Contribution

It introduces a controllable technique to engineer flat bands in folded graphene using strain via nano origami, allowing tunable flat band structures and correlated states.

Findings

Tunable pseudo-magnetic fields in folded graphene.

Observation of correlation-induced flat band splits.

Adjustable flat band geometry via edge-width control.

Abstract

Flat electronic bands with tunable structures offer opportunities for the exploitation and manipulation of exotic interacting quantum states. Here, we present a controllable route to construct easily tunable flat bands in folded graphene, by nano origami-controlled strain engineering, and discover correlated states in this system. Via tearing and folding graphene monolayer at arbitrary step edges with scanning tunneling microscope manipulation, we create strain-induced pseudo-magnetic fields as well as resulting flat electronic bands in the curved edges of folded graphene. We show that the intensity of the pseudo-magnetic field can be readily tuned by changing the width of the folding edge due to the edge-width-dependent lattice deformation, leading to the well adjustability of the geometry of flat bands in folded graphene. Furthermore, by creating expected dispersionless flat bands using this technique, the correlation-induced splits of flat bands are successfully observed in the density of states when these bands are partially filled. Our experiment provides a feasible and effective pathway to engineer the system with tunable flat band structures, and establishes a new platform that can be used to realize devisable strain and interaction induced quantum phases.