Valley-filters using kink states in bilayer graphene

Abstract

The topic of this thesis is on quantum transport calculations through so-called ‘kink’states in graphene systems. These states allow us to filter electrons according to their valley index. The valley index is a quantum number that exists in graphene systems. It has two configurations similar to the electron spin. The kink states only allow electrons from one of the two valleys to pass, while electrons from the other valley are not allowed to enter the state. We use these kink states to calculate the transport properties of three different mesoscopic devices: the valley filter, the valley valve and the valley-Y junction.The valley filter only allows electrons from one valley to pass and creates a valley polarised current. The valley valve consists of two valley filters connected in series. By changing which valley electrons can enter the second filter, we can control the current through this device. An electron can either pass through the valley valve or not. In the valley Y-junction, the different electron channels form a Y. This device creates two oppositely polarised electron currents from an unpolarised current.