Bose Einstein Condensate in a polymer at room temperature has potential for faster optoelectronics and new lasers other applications

Researchers at IBM’s Binnig and Rohrer Nano Center have demonstrated a complex quantum mechanical phenomenon known as Bose-Einstein condensation (BEC), using a luminescent polymer (plastic) similar to the materials in light emitting displays used in many of today’s smartphones.

This discovery has potential applications in developing novel optoelectronic devices including energy-efficient lasers and ultra-fast optical switches — critical components for powering future computer systems to process massive Big Data workloads. The use of a polymer material and the observation of BEC at room temperature provides substantial advantages in terms of applicability and cost.

Another application for BEC is for the building of so-called atom lasers, which could have applications ranging from atomic-scale lithography to measurement and detection of gravitational fields.

Nature Materials – Room-temperature Bose–Einstein condensation of cavity exciton–polaritons in a polymer

In the experiment, a thin polymeric layer is placed between two mirrors and excited with laser light. This thin plastic film is approximately 35 nanometers thick, for comparison a sheet of paper is about 100,000 nanometers thick. The bosonic particles are created through interaction of the polymer material and light which bounces back and forth between the two mirrors.

The phenomenon only lasts for a few picoseconds (one trillionth of a second), but the scientists believe this is already long enough to use the bosons to create a source of laser-like 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 ultra-pure crystals defied our expectations,” said Dr. Thilo Stoferle, 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 next step for scientists is to study and control the extraordinary properties of the Bose-Einstein Condensate and to evaluate possible applications including analog quantum simulations. Such simulations could be used to model very complex scientific phenomena such as superconductivity, which is difficult using today’s computational approaches.

ABSTRACT

A Bose–Einstein condensate (BEC) is a state of matter in which extensive collective coherence leads to intriguing macroscopic quantum phenomena. In crystalline semiconductor microcavities, bosonic quasiparticles, known as exciton–polaritons, can be created through strong coupling between bound electron–hole pairs and the photon field. Recently, a non-equilibrium BEC and superfluidity have been demonstrated in such structures. With organic crystals grown inside dielectric microcavities, signatures of polariton lasing have been observed. However, owing to the deleterious effects of disorder and material imperfection on the condensed phase only crystalline materials of the highest quality have been used until now. Here we demonstrate non-equilibrium BEC of exciton–polaritons in a polymer-filled microcavity at room temperature. We observe thermalization of polaritons and, above a critical excitation density, clear evidence of condensation at zero in-plane momentum, namely nonlinear behaviour, blueshifted emission and long-range coherence. The key signatures distinguishing the behaviour from conventional photon lasing are presented. As no crystal growth is involved, our approach radically reduces the complexity of experiments to investigate BEC physics and paves the way for a new generation of opto-electronic devices, taking advantage of the processability and flexibility of polymers.

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