Magnetic field driven nano tippe top

Abstract

We investigate the motion of a nano tippe top, which is formed from a C60 fullerene, and which is assumed to be spinning on either a graphene sheet or the interior of a single-walled carbon nanotube. We assume no specific geometric configuration for the top, however for example, the nano tippe top might be formed by joining a fullerene C60 with a small segment of a smaller radius carbon nanotube. We assume that it is spinning on a graphene sheet or a carbon nanotube surface only as a means of positioning and isolating the device, and the only effect of the graphene or the carbon nanotube surface is only through the frictional effect generated at the point of the contact. We employ the same basic physical ideas originating from the classical tippe top and find that the total retarding force, which comprises both a frictional force and a magnetic force at the contact point between the C60 fullerene and the graphene sheet or the inner surface of the single-walled carbon nanotube, induces the C60 molecule to spin and precess from a standing up position to a lying down position. Unlike the classical tippe top, the nanoscale tippe top does not flip over since the gravitational effect is not sufficient at the nano scale. After the precession, while the molecular top spins about its lying down axis, if we apply the opposite retarding magnetic force at the contact point, then the molecule will return to its standing up position. The standing up and the lying down configurations of the nano tippe top during the precession and retraction processes demonstrate its potential use as a memory device in nano-computing.