Optomechanics : Semiconductor Supercooled By Heating!

Ever thought of reaching absolute zero temperature? There are methods to achieve it but they were until now limited only to gases. Scientists have earlier been successful in LASER cooling of atoms but this is perhaps the first time that semiconductors are cooled in similar way. Researchers at Københavns Universitet – Københavns Universitet have developed method to cool semiconductor to about 4K that too by heating it up!

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Image Credit: Niels Bohr Institute

In what can be termed as a beautiful combination of Quantum mechanics and nano physics, Niels Bohr Institute team created semiconductor membrane of 160nm thick and of surface area 1mm². Koji Usami, an associate professor at Quantop at the Niels Bohr Institute wanted to see the extent of application of quantum mechanics. However, the right material for achieving it was a difficult thing for his team. Now with the semiconductor membrane constructed, the team at Niels Bohr institute experimented successfully.

In the experiment, the team thought of creating an #-Link-Snipped-# by placing the said semiconductor membrane in box made up of mirrors. #-Link-Snipped-# was then made to strike the material in vacuum. As per the natural laws, some of the light was absorbed while some of it was reflected. The reflected light struck again and again, hence creating optical resonator. This absorption led to changing distances between the membrane layers thereby creating fluctuations between mirror and semiconductor membrane. These changing distances led the material cool at particular oscillations.

The scientists had a control over the optical source all the time and could control the process externally. The work by Niels Bohr team is published in Nature Physics. At the end, Usami and his team reached a temperature of minus 269 Deg C.

The process designed by the group might be used effectively in cooling #-Link-Snipped-#. The method will also find wide applications in sensor technology. The sensors are expected to be a next big thing in measuring mechanical forces and electric current!