The passage of electrons in materials determines their electrical characteristics. When a voltage is applied to a conducting substance, electrons begin to flow, resulting in an electrical current. These electrons are commonly assumed to move in straight lines along the electric field, similar to a ball rolling down a hill. However, these are not the only possible electron trajectories: when a magnetic field is introduced, electrons no longer travel in straight lines along the electric field but instead curve. The twisted electrical fluxes produce transverse signals known as "Hall" responses.
According to a team of researchers, circularly polarised light can create bent electronic fluxes in bilayer graphene. Now it may be possible to bend electrons without the need for a magnetic field. The development would be incredible for Graphene Market, which would lead to new detecting and imaging technologies related to graphene.
Electrons are more than just particles; they can also have a quantum wave-like character. The wave pattern of electrons in quantum materials, such as bilayer graphene, can exhibit a complicated winding, referred to as quantum geometry.
Bilayer graphene has two pockets of electron valleys (K and K'). When an electric field is applied perpendicularly, the quantum geometrical features of electrons in these two valleys can lead them to bend in opposite directions. As a result, their Hall effects are neutralised.
The researchers discovered that they could selectively stimulate one specific valley population of electrons in the material. This was done by shining circular polarised infrared light onto a bilayer graphene device. Thus, resulting in photovoltage perpendicular to the normal electron flow.
Further, the team has constructed and configured the device in such a way that current only flows when light is illuminated. This advancement is essential because conventional photodetectors frequently require enormous voltage biases, which can result in "black currents" that flow even when no light is present. The group avoided the background noise that interfered with experiments. It helped them obtain detection sensitivity several orders of magnitude higher than any other 2D material.
The study's findings open up a new world of detection and imaging possibilities. This is mainly because bilayer graphene can be changed from semimetal to semiconductor with a very small bandgap, allowing it to detect photons with deficient energy. Such a discovery could have significant ramifications in infrared and terahertz sensing applications. It may also be beneficial for imaging in space, medical imaging, such as for tissue skin cancer, or even security applications such as material quality checking.