Excited photo-emitters can cooperate and radiate simultaneously, a phenomenon called superfluorescence. Researchers from Empa and ETH Zurich, together with colleagues from IBM Research Zurich, have recently been able to create this effect with long-range ordered nanocrystal superlattices. This discovery could enable future developments in LED lighting, quantum sensing, quantum communication and future quantum computing. The study has just been published in the renowned journal "Nature".
Some materials spontaneously emit light if they are excited by an external source, for instance a laser. This phenomenon is known as fluorescence. However, in several gases and quantum systems a much stronger emission of light can occur, when the emitters within an ensemble spontaneously synchronize their quantum mechanical phase with each other and act together when excited.
In this way, the resulting light output can be much more intense than the sum of the individual emitters, leading to an ultrafast and bright emission of light – superfluorescence. It only occurs, however, when those emitters fulfill stringent requirements, such as having the same emission energy, high coupling strength to the light field and a long coherence time.
As such, they are strongly interacting with each other but at the same time are not easily disturbed by their environment. This has not been possible up to now using technologically relevant materials. Colloidal quantum dots could just be the ticket; they are a proven, commercially appealing solution already employed in the most advanced LCD television displays – and they fulfill all the requirements.
Researchers at Empa and ETH Zurich, led by Maksym Kovalenko, together with colleagues from IBM Research Zurich, have now shown that the most recent generation of quantum dots made of lead halide perovskites offer an elegant and practically convenient path to superfluorescence on-demand.
For this, the researchers arranged perovskite quantum dots into a three-dimensional superlattice, which enables the coherent collective emission of photons – thus creating superfluorescence. This provides the basis for sources of entangled multi-photon states, a missing key resource for quantum sensing, quantum imaging and photonic quantum computing.
“Birds of a feather flock together”
A coherent coupling among quantum dots requires, however, that they all have the same size, shape and composition because “birds of a feather flock together” in the quantum universe, too. “Such long-range ordered superlattices could only be obtained from a highly monodisperse solution of quantum dots, the synthesis of which had been carefully optimized over the last few years,” said Maryna Bodnarchuk, a senior scientist at Empa.
With such ”uniform” quantum dots of various sizes, the research team could then form superlattices by properly controlling the solvent evaporation.
The final proof of superfluorescence came from optical experiments performed at temperatures of around minus 267 degrees Celsius. The researchers discovered that photons were emitted simultaneously in a bright burst: “This was our ‘Eureka! ‘ moment. The moment we realized that this was a novel quantum light source,” said Gabriele Rainó from ETH Zurich and Empa who was part of the team that carried out the optical experiments.
The researchers consider these experiments as a starting point to further exploit collective quantum phenomena with this unique class of material.
“As the properties of the ensemble can be boosted compared to just the sum of its parts, one can go way beyond engineering the individual quantum dots,” added Michael Becker from ETH Zurich and IBM Research.
The controlled generation of superfluorescence and the corresponding quantum light could open new possibilities in LED lighting, quantum sensing, quantum-encrypted communication and future quantum computing.
Prof. Dr. Maksym Kovalenko
Empa, Thin Films and Photovoltaics
ETH, Functional Inorganic Materials
Phone +41 58 765 4557
Dr. Maryna Bodnarchuck
Empa, Thin Films and Photovoltaics
Phone +41 58 765 59 40
Dr. Gabriele Rainò
ETH Zurich, Laboratory of Inorganic Chemistry
Phone +41 44 633 09 97
Dr. Thilo Stöferle
IBM Research – Zurich
Phone +41 44 724 85 01
G Raino, MA Becker, MI Bodnarchuck, RF Mahrt, MV Kovalenko, T Stöferle; Superfluorescence from Lead Halide Perovskite Quantum Dot Superlattices; Nature, DOI: 10.1038/s41586-018-0683-0
Rainer Klose | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt
New method for simulating yarn-cloth patterns to be unveiled at ACM SIGGRAPH
09.07.2020 | Association for Computing Machinery
Virtual Reality Environments for the Home Office
09.07.2020 | Universität Stuttgart
New insight into the spin behavior in an exotic state of matter puts us closer to next-generation spintronic devices
Aside from the deep understanding of the natural world that quantum physics theory offers, scientists worldwide are working tirelessly to bring forth a...
Kiel physics team observed extremely fast electronic changes in real time in a special material class
In physics, they are currently the subject of intensive research; in electronics, they could enable completely new functions. So-called topological materials...
Solar cells based on perovskite compounds could soon make electricity generation from sunlight even more efficient and cheaper. The laboratory efficiency of these perovskite solar cells already exceeds that of the well-known silicon solar cells. An international team led by Stefan Weber from the Max Planck Institute for Polymer Research (MPI-P) in Mainz has found microscopic structures in perovskite crystals that can guide the charge transport in the solar cell. Clever alignment of these "electron highways" could make perovskite solar cells even more powerful.
Solar cells convert sunlight into electricity. During this process, the electrons of the material inside the cell absorb the energy of the light....
Empa researchers have succeeded in applying aerogels to microelectronics: Aerogels based on cellulose nanofibers can effectively shield electromagnetic radiation over a wide frequency range – and they are unrivalled in terms of weight.
Electric motors and electronic devices generate electromagnetic fields that sometimes have to be shielded in order not to affect neighboring electronic...
A promising operating mode for the plasma of a future power plant has been developed at the ASDEX Upgrade fusion device at Max Planck Institute for Plasma...
07.07.2020 | Event News
02.07.2020 | Event News
19.05.2020 | Event News
10.07.2020 | Life Sciences
10.07.2020 | Materials Sciences
10.07.2020 | Life Sciences