Switching spin filling sequence in a bilayer graphene quantum dot through trigonal warping

TL;DR

This paper shows how to control the electron shell structure and spin filling sequence in a bilayer graphene quantum dot by tuning the trigonal warping effect with electrical gating, enabling spin manipulation.

Contribution

It introduces a method to switch the spin filling sequence in a bilayer graphene quantum dot via electrical control of trigonal warping effects.

Findings

Switchable electron shell structure achieved.

Spin filling sequence can be altered with electric field.

Trigonal warping enables spin degree of freedom manipulation.

Abstract

We demonstrate a switchable electron shell structure in a bilayer graphene quantum dot by manipulating the trigonal warping effect upon electrical gating. Under a small perpendicular electric field, the lowest s-shell is sequentially filled with two spin-up and two spin-down electrons of opposite valleys. When increasing the electric field, an additional three-fold minivalley degeneracy is generated so that the s-shell can be filled with 12 electrons with the first/last 6 electrons having the same spin polarization. The switched spin filling sequence demonstrates the possibility of using the trigonal warping effect to electrically access and manipulate the spin degree of freedom in bilayer graphene.