| Oct 31, 2012 |
Graphene mini-lab
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(Nanowerk News) A team of physicists from Europe and South Africa showed that electrons moving randomly in graphene can mimic the dynamics of particles such as cosmic rays, despite travelling at a fraction of their speed, in a paper about to be published in EPJ B ("Relativistic Brownian motion on a graphene chip").
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Andrey Pototsky and colleagues made use of their knowledge of graphene, which is made of a carbon layer, one atom thick, and packed in a honeycomb lattice pattern. In such material the interaction of electrons with atoms changes the effective mass of the electrons. As a result, the energy of electrons in graphene becomes similar to the photon energy.
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Therefore, electrons in graphene can be regarded as behaving like cosmic rays, which belong to a family known as ultra-relativistic particles, even though their actual velocity is one hundred times lower than the speed of light.
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The authors employed the classical equations used to describe random motion—so-called Brownian motion—to study the dynamics of electrons within the confines of their graphene mini-laboratory. They considered different graphene chip geometries and subjected them to changing conditions that affect the way these electrons diffuse through the material, such as temperature and electric field strength.
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Going one step further, the authors were able to rectify electron fluctuations and to control the electron motion itself, from an unusual chaotic type of motion to a periodic movement, by varying the electric field.
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Future work would experimentally demonstrate how variation of the temperature can be used positively to enhance the performance of graphene chips by gaining a greater control over electron transport. Such graphene mini-labs could also ultimately help us to understand the dynamics of matter and anti-matter in cosmic rays.
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