Femtosecond Control of Electrons

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Researchers from University of Erlangen-Nuremberg used ultra-short laser impulses to precisely control electrons in graphene

Graphene is a two-dimensional semi-metal and the material’s single atom layer is thin enough to let light penetrate to set electrons in motion. Researchers at the Chair for Laser Physics demonstrated generation of an electric signal in one femtosecond with the help of a very short laser pulse. Now a team of researchers from University of Erlangen-Nuremberg focused a second laser pulse at this light-driven wave. The team found that the second pulse allows electron wave to pass through graphene. The second laser pulse is capable of deflecting, accelerating, or even changing the direction of the electron wave in order to transmit information. Moreover, the transmission depends on the exact time, strength, and direction of the second pulse.

According to the researchers, electron wave is analogous to a wave in water. The split in water waves is attributed to an obstacle and converge and interfere when the waves pass the obstacle. The waves either amplify or cancel each other and this relies on how the sub-waves stand in relation to one another. According to Christian Heide from the Chair of Laser Physics, the second laser pulse can be used to modify the individual sub-waves in a targeted manner in order to control their interference. Quantum phenomena such as the wave characteristics of electrons are challenging to control as it is very difficult to maintain the electron wave in a material. This in turn is attributed to scattering of electron wave with other electrons to lose its wave characteristics.

These experiments are usually performed at extremely low temperatures. However, the team performed these experiments at room temperature as it is possible to control electrons using laser pulses. Moreover, the high speed of lasers suggests that no time is left for the scatter processes with other electrons. This in turn allows to study several new physical processes that were previously not accessible. The research titled as: ‘Coherent Electron Trajectory Control in Graphene’ was published in the journal Physical Review Letters on November 14, 2018.

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Cynthia Carrier is a graduate of Texas A&M, where she played volleyball and annoyed a lot of professors. Now as Plains Gazette's entertainment and Lifestyle Editor, she enjoys writing about delicious BBQ, outrageous style trends and all things Texas.