First time wavelike behavior of room-temp polariton condensate has been demonstrated in the lab on a macroscopic length scale: a significant development in understanding and manipulation of quantum objects.
Quantum mechanics tells us objects have both particle and wavelike behaviour with a wavelength inversely proportional to the object’s velocity…at atomic length scales, except with bosons, particles of a particular type that can be combined in large numbers in the same quantum state, it is possible to form macroscopic-scale quantum objects, called Bose-Einstein condensates. These are at the root of quantum physics’ superfluidity and superconductivity. Their scientific importance nearly 70 yrs after their existence was theorized, earning Eric Cornell, Wolfgang Ketterle, Carl Wieman the Nobel Prize in Physics, 2001.
Placing particles in the same state to obtain a condensate normally requires the temperature to be lowered to a level near 0K.
To produce the room-temperature condensate, the team from Polytechnique and Imperial College 1st created a device that makes it possible for polaritons – hybrid quasi-particles: part light/ part matter – to exist. The device is composed of a film of organic molecules 100 nm thick, confined between 2 nearly perfect mirrors. The condensate is created by exciting a sufficient number of polaritons using a laser and then observed via the blue light it emits.
“To date, the majority of polariton experiments continue to use ultra-pure crystalline semiconductors,” says Prof Kéna-Cohen. “Our work demonstrates that it is possible to obtain comparable quantum behaviour using ‘impure’ and disordered materials such as organic molecules. This has the advantage of allowing for much simpler and lower-cost fabrication.”
Besides observing the organic polariton condensate’s wavelike behaviour, the experiment showed condensate size could not exceed approximately 100 micrometres before it destroy itself, fragmenting and creating vortices.
In a condensate, the polaritons all behave the same way, like photons in a laser. Applications for room-temp condensates: future polariton micro-lasers using low-cost organic materials, powerful transistors entirely powered by light. Challenge in developing such applications will be to obtain a lower particle-condensation threshold so external laser used for pumping could be replaced by more practical electrical pumping.
Professor Kéna-Cohen concludes: “One fascinating aspect, for example, is the extraordinary transition between the state of non-condensed particles and the formation of a condensate. On a small scale, the physics of this transition resemble an important step in the formation of the Universe after the Big Bang.” http://www.polymtl.ca/carrefour/en/article.php?no=4688
To produce the room-temperature condensate, the team of researchers created a device that makes it possible for polaritons to exist. The device has a film of organic molecules 100 nanometres thick, between 2 nearly perfect mirrors. The condensate is created by first exciting a sufficient number of polaritons using a laser and then observed via the blue light it emits. Its dimensions can be comparable to that of a human hair, a gigantic size on the quantum scale. Credit: Konstantinos Daskalakis, Imperial College London.
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