Twisting or untwisting graphene twisted nanoribbons without rotation

TL;DR

This paper introduces a novel, tension-free method to twist or untwist graphene nanoribbons by adjusting substrate distance, avoiding the need for rotation, and demonstrates its feasibility through molecular dynamics simulations.

Contribution

It presents an innovative approach to control twist in graphene nanoribbons without rotation, expanding possibilities for nanoscale mechanical manipulation.

Findings

Twist can be added or removed by changing substrate separation.

The method is tension-free and does not require end-to-end distance control.

The process aligns with the linking number theorem of space curves.

Abstract

The common sense regarding twisting or untwisting a ribbon is that it requires the application of an external rotation to happen. However, at nanoscale, the application of precise amounts of rotation on a nanoribbon is not a trivial task. Here, the concept of an alternative method to add twist to or remove twist from a twisted graphene nanoribbon (TGNR) without rotation is presented. The method consists of suspending a TGNR on two separate substrates and by changing only their distance, the total amount of twist of the TGNR is shown to change. The possibility to fine-tuning the amount of twist of a TGNR is also shown. The concept is demonstrated through fully atomistic molecular dynamics simulations and numerical calculations of the topological parameters twist and writhe of a TGNR. It is shown that the above process satisfies the so-called linking number theorem of space curves. Besides being experimentally feasible, this concept reveals a new kind of twist to writhe transition phenomenon that is tension-free and does not require controlling neither the nanoribbon end-to-end distance nor its critical twist density.