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Bose-Einstein Condensate Formed in Record-Breaking Time

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ESPOO, Finland, July 10, 2020 — Researchers at Aalto University and the University of Eastern Finland have created a Bose-Einstein condensate in femtoseconds (fs) — a record-breaking time for producing this state of matter.

Bose-Einstein condensation is a quantum phenomenon in which a large number of particles start to behave as if they were one. In the quantum, just as in the classical world, particles must first lose their energy in order to condense to the lowest possible energy state. This process typically takes from thousandths to trillionths of a second.

The researchers combined a lattice of plasmonic nanoparticles with dye molecule solution at the strong coupling regime and pumped the molecules optically. The emitted light revealed three distinct regimes: one-dimensional lasing, incomplete stimulated thermalization, and two-dimensional multimode condensation.

World's fastest Bose-Einstein condensate, Aalto University.

The sample (inside a glass side). Courtesy of Aaro Väkeväinen and Konstantinos Daskalakis/Aalto University.
 

The researchers showed that formation of a condensate with a pronounced thermal distribution was possible at a 200-fs timescale. They attributed this fast thermalization to partially coherent dynamics due to highly stimulated processes and strong light-matter coupling. “This means that the effective interaction of photons, which leads into condensation, accelerates when the number of photons increases,” researcher Aaro Väkeväinen said. “Such a phenomenon is the key for the speed-up.” The condensate was achieved by matching the thermalization rate with the lattice size and occurred only for pump pulse durations below a critical value.

The results of the experiments provide a method to control and monitor thermalization processes and condensate formation at a subpicosecond timescale.


Many different systems have been used to observe Bose-Einstein condensates, but none have demonstrated the speed of the Finnish researchers’ condensate. It was challenging for the team to prove that condensation happened as quickly as it did, since even advanced lab cameras could not measure the time resolution. “When we pumped energy into the molecules in 50 fs, the condensate was observed. But with 300-fs pump pulse we did not see it, which indicated that the condensation must be triggered even faster,” researcher Antti Moilanen said.

World's fastest Bose-Einstein condensate, Aalto University.

The intensity of the light emitted by the condensate shows a distribution in energy that matches the predictions by Bose and Einstein. The formation of the condensate occurred in a few hundreds of femtoseconds. Courtesy of Aalto University/Sofia Heikkinen.

“The condensate produces a coherent light beam that is 100,000 times brighter than the first surface plasmon polariton condensate we observed in a metal nanorod array two years ago,” professor Päivi Törmä said. The large number of photons in the beam allowed the researchers to clearly observe the distribution of photons at different energies, as predicted by Bose and Einstein almost 100 years ago. “The brightness of the beam makes it easier to explore new areas of fundamental research and applications with these condensates,” Törmä said.

An invention that emerged from the group’s condensate research has been granted a patent and will be further developed.

The research was published in Nature Communications (www.doi.org/10.1038/s41467-020-16906-1). 

Published: July 2020
Glossary
bose-einstein condensate
A Bose-Einstein condensate (BEC) is a state of matter that forms at temperatures close to absolute zero. It is named after Satyendra Nath Bose and Albert Einstein, who independently predicted the existence of such a state in the 1920s. BEC is a unique and fascinating form of matter that exhibits macroscopic quantum phenomena. In a Bose-Einstein condensate, some key factors to consider are: Temperature: BEC forms at extremely low temperatures, typically in the nanokelvin (billionths of a...
nano
An SI prefix meaning one billionth (10-9). Nano can also be used to indicate the study of atoms, molecules and other structures and particles on the nanometer scale. Nano-optics (also referred to as nanophotonics), for example, is the study of how light and light-matter interactions behave on the nanometer scale. See nanophotonics.
nanophotonics
Nanophotonics is a branch of science and technology that explores the behavior of light on the nanometer scale, typically at dimensions smaller than the wavelength of light. It involves the study and manipulation of light using nanoscale structures and materials, often at dimensions comparable to or smaller than the wavelength of the light being manipulated. Aspects and applications of nanophotonics include: Nanoscale optical components: Nanophotonics involves the design and fabrication of...
plasmonics
Plasmonics is a field of science and technology that focuses on the interaction between electromagnetic radiation and free electrons in a metal or semiconductor at the nanoscale. Specifically, plasmonics deals with the collective oscillations of these free electrons, known as surface plasmons, which can confine and manipulate light on the nanometer scale. Surface plasmons are formed when incident photons couple with the conduction electrons at the interface between a metal or semiconductor...
quantum
The term quantum refers to the fundamental unit or discrete amount of a physical quantity involved in interactions at the atomic and subatomic scales. It originates from quantum theory, a branch of physics that emerged in the early 20th century to explain phenomena observed on very small scales, where classical physics fails to provide accurate explanations. In the context of quantum theory, several key concepts are associated with the term quantum: Quantum mechanics: This is the branch of...
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