Electric-field-induced spin spiral state in bilayer zigzag graphene nanoribbons

TL;DR

This paper explores how electric fields induce spin spiral states in bilayer zigzag graphene nanoribbons, revealing size-dependent magnetic phase transitions and the role of spin stiffness at low temperatures.

Contribution

It introduces a novel analysis of electric-field-induced spin spirals in graphene nanoribbons using the generalized Bloch theorem, highlighting size and thickness effects.

Findings

Large ribbons exhibit spiral states at certain electric fields.

Spin spiral states are more rapidly formed with increased thickness.

The spin stiffness reduction drives the transition to spiral states.

Abstract

We investigated the emergence of spin spiral ground state induced by the electric field in the bilayer zigzag graphene nanoribbons for the ferromagnetic edge states. To do that, we employed the generalized Bloch theorem to create flat spiral alignments for all the magnetic moments of carbon atoms at the edges within a constraint scheme approach. While the small ribbon width can preserve the ferromagnetic ground state, the large one shows the spiral ground state starting from a certain value of the electric field. We also pointed out that the spiral ground state is caused by the reduction of spin stiffness. In this case, the energy scale exhibits a subtle nature that can only be considered at the low temperature. For the last discussion, we also revealed that the spin spiral ground state appears more rapidly when the thickness increases. Therefore, we justify that the large ribbon width and large thickness can generate many spiral states induced by the electric field.