&Bullet; physics 14, s80
When studying the current flowing in bilayer graphs, the researchers have isolated electron jets associated with specific valley states.
The electrons in graphene – and in other 2D materials – can be in one of two momentum states or “valleys”. Researchers are interested in controlling these valley states in order to store and process information within the states. One difficulty in achieving this goal is primarily to generate valley polarized currents. Carolin Gold from the Swiss Federal Institute of Technology (ETH) in Zurich and her colleagues have now found a way to isolate a pair of electron jets – one for each valley – in a graphene double layer  . The technology could one day be integrated into “valleytronic” devices in order to sort electrons according to their valley state.
Normally the valley states in graphs are indistinguishable, but under certain circumstances the electronic band structure becomes asymmetrical or “trigonal distorted”, resulting in unique momentum profiles for each valley. Theorists predicted that this fault would create multiple valley-polarized jets that flow in different directions along a single sheet of graphene. But isolating these jets has proven difficult.
Gold and her colleagues used a sheet of two-layer graphene that they predicted would also house valley-polarized jets. They placed two metallic gates on the double layer, separated by a small channel 50 nm wide. They applied a voltage to the double layer and measured the current flowing through the opening. They mapped the path of this current with a metallic tip that generates an interfering signal when the current is measured. The data showed a pair of jets going through an angle of. are separated
as expected from theoretical models.
Michael Schirber is the corresponding editor for physics based in Lyon, France.
- C. Gold et al., “Coherent jetting from a gate-defined channel in bilayer graphs”, Phys. Rev. Lett.127, 046801 (2021).