Ultrafast control over electron pulses

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Nr. 126/2014 - 02.07.2014

Physicists at the University of Göttingen control current flow in nanostructures with terahertz fields

(pug) The rapid-paced improvement in the performance of modern electronics, like those used in smartphones, is based on increasingly smaller and faster computer chips. For the first time, researchers at Göttingen University have now demonstrated on metallic nanotips that they can actively control currents at terahertz frequencies – 1000 billion cycles per second. Currently, the speed of computer processors is given in gigahertz or the equivalent of one billion cycles per second. To propel future speeds into the terahertz range, entirely new technologies are needed which can't help but lead from electronics to optics. Novel concepts emanating from what is called light-wave electronics that the researchers in Göttingen are working with employ controlled light fields and extremely short laser pulses to govern electron currents on the nanoscale. The results have been published in the journal Nature Physics.

In their experiments, the research group around Professor Claus Ropers at the Faculty of Physics superimposed light pulses and electrical terahertz pulses and observed their coupling. “The data from the measurement gives us a direct reading of the electrical response of the nanostructure to the ultrashort input signal. This lets us observe how the current strength and the speed of electrons follow ultrafast terahertz transients at the nanotip without delay,” explains doctoral candidate Lara Wimmer.

Even though a number of physical hurdles will have to be overcome before terahertz frequencies are used in computer chips, direct application possibilities are already emerging from the current results in ultrafast spectroscopy and imaging, one focus of this research group. Doctoral candidate Georg Herink explains, “The unique electron dynamics in the terahertz field allows fine tuning of the speed distribution in an electron pulse. This optimisation is aimed at the shortest pulses for time-resolved electron microscopy, which we are developing with our colleagues here in Göttingen.“

Original publication: Lara Wimmer et al.: Terahertz control of nanotip photoemission, Nature Physics 10, 432–436 (2014), doi: http://dx.doi.org/10.1038/nphys2974

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