|Graphene Mini-Lab (Vol. 44 No. 1)|
Dirac electron diffusion (represented by a red semi classical trajectory) on a ratchet asymmetric potential represented by blue triangles can be rectified by ac drives.
A mini-laboratory is proposed to study fast moving electrons in the carbon-based material called graphene as a model for massless particles moving in a noisy environment with velocities close to the speed of light, in analogy to relativistic Brownian particles such as cosmic rays.
In graphene (one atom-thick carbon layer forming a honeycomb lattice) the interaction of electrons with atoms changes the effective mass of the electrons. As a result, the energy of these electrons becomes similar to the photon energy. Therefore, electrons in graphene can be regarded as ultra-relativistic particles even though their actual velocity is 100 times lower than the speed of light.
The authors used the classical Brownian motion formalism to study the dynamics of electrons within the confines of the graphene mini-laboratory. They considered different chip geometries AND subjected them to changing conditions affecting the way these electrons diffuse through the material such as temperature and electric field strength.
Going one step further, the authors were able to rectify electron fluctuations and to control the electron motion itself from an unusual chaotic to a periodic motion by varying the electric field. Future work would experimentally demonstrate how variation of the temperature could 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 understand the dynamics of matter and anti-matter in cosmic rays.
A. Pototsky, F. Marchesoni, F. V. Kusmartsev, P. Hanggi and S. E. Savel'ev, ‘Relativistic Brownian motion on a graphene chip’, Eur. Phys. J. B (2012) 85: 356