Instead of the usual ultrapure crystals, a plastic film similar to the material used in light-emitting smartphone displays has been used to demonstrate a complex quantum mechanical phenomenon.
The first-time demonstration of a Bose-Einstein condensation (BEC) at room temperature using a luminescent polymer, achieved by scientists at IBM Research, has potential applications in the development of novel optoelectronic devices, such as energy-efficent lasers and ultrafast optical switches. Such components are critical for powering the future computer systems needed to process massive Big Data workloads, and using the polymer material would be less costly and easier to apply.
Polariton BEC within the polymer-filled microresonator consisting of the luminescent polymer layer (yellow) and two mirrors, each consisting of many pairs of different transparent oxide layers (red and blue). The polaritons are created by excitation of the polymer layer from below with a laser beam (white). The polaritons (green), which are bosons composed of photons and electron-hole pairs, are formed through interactions of the polymer with the microcavity. Once a critical density is reached, the polaritons undergo Bose-Einstein condensation, emitting green laserlike light through the top mirror. Images courtesy of IBM Research.
A Bose-Einstein condensate is a peculiar state of matter that occurs when a dilute gas of particles (bosons) are cooled to nearly absolute zero (-273 °C, -459 °F). At this temperature, intriguing macroscopic quantum phenomena occur in which the bosons all line up like ballroom dancers. The phenomenon is named after scientists Satyendra Nath Bose and Albert Einstein, who first predicted it in the mid-1920s, although it was only experimentally proved in 1995 at those extreme temperatures.
The IBM team said it has achieved the same state at room temperature using a thin noncrystalline polymer film developed by chemists at the University of Wuppertal in Germany.
The IBM scientists who achieved the Bose-Einstein condensate breakthrough are (l-r): Lijian Mai, Rainer F. Mahrt and Thilo Stöferle.
The scientists placed a 35-nm-thick polymeric layer between two mirrors and excited it with laser light. The bosonic particles are created through interaction of the polymer material and light, which bounces back and forth between the mirrors.
The phenomenon lasts only a few picoseconds, but the scientists believe that this is already long enough to use the bosons to create a source of laserlike light and/or an optical switch for future optical interconnects. These components are important building blocks to control the flow of information in the form of zeroes and ones between future chips and can significantly speed up their performance while using much less energy.
“That BEC would be possible using a polymer film instead of the usual ultrapure crystals defied our expectations,” said Dr. Thilo Stöferle, a physicist at IBM Research. “It’s really a beautiful example of quantum mechanics, where one can directly see the quantum world on a macroscopic scale.”
The liquid form of the polymer is placed by a laser, altering its color.
The next step is to study and control the BEC’s extraordinary properties and to evaluate possible applications, including analog quantum simulations. The simulations could be used to model very complex scientific phenomena such as superconductivity, which is difficult using today’s computational approaches.
The research, conducted in the Binnig and Rohrer Nanotechnology Center at IBM Research-Zurich, was funded under the European Union’s FP7 Project ICARUS, which has the goal of creating and characterizing new hybrid-semiconductor systems and implementing them in photonic and optoelectronic devices.
A paper on the work, “Room-temperature Bose–Einstein condensation of cavity exciton–polaritons in a polymer,” by Johannes D. Plumhof et al, appears in Nature Materials doi: 10.1038/nmat3825.