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Novel light sources made of 2D materials.

Two-photon sources are particularly well suited for tap-proof data encryption.

Physicists from the University of Wurzburg have designed a light source that emits photon pairs. The experiment's key ingredients: a semiconductor crystal and some sticky tape.

So-called monolayers--solid materials of minimum thickness --are at the heart of the research. These "super materials" show great promise to revolutionise many areas of physics. In two-dimensional form, they freguently exhibit unexpected properties that make them interesting for research. The so-called transition metal dichalcogenides (TMDC)are particularly promising. They behave like semiconductors and can be used to manufacture ultra-small and energy-efficient chips, for example. Moreover, TMDCs are capable of generating light when supplied with energy.

Dr Christian Schneider, Professor Sven Hofling and their research team from the Chair of Technical Physics of the Julius-Maximilians-Universitat Wurzburg (JMU) in Bavaria, Germany, have harnessed exactly this effect for their experiments.

First, a monolayer was produced using a simple method. This usually involves a piece of sticky tape to peel a multi-layer film from a TMDC crystal in a first step. Using the same procedure, thinner and thinner layers can be stripped from this film. This process is repeated until the material on the tape is only one layer thick.

The researchers then cooled this monolayer down to a temperature of just above absolute zero and excited it with a laser. This causes the monolayer to emit single photons under specific conditions. "We were now able to show that a specific type of excitement produces not one but exactly two photons," Schneider explained. "The light particles are generated in pairs so to speak."

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Publication:Environmental Engineering
Date:Dec 1, 2016
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