Researchers from the University at Buffalo developed a way to identify the electronic properties of individual graphene sheets in a stack of graphene sheets. The method works even when the sheets are covering each other up.

The idea is to shoot a beam of infrared light on the graphene stack, and measure how the light polarization (direction of oscillation) changes when it bounces back from the graphene sheets. The researchers say the new technique is ultra sensitive and it allowed them to examine dozens of sheets in a single stack.

It turns out that graphene's absorption and emission patterns change when a magnetic field is applied, which means that scientists can turn the polarization of light on and off either by applying a magnetic field to graphene layers or, more quickly, by applying a voltage that sends electrons flowing through the graphene. This discovery could lead to applications in communications, imaging and signal processing.

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