Researchers from the Donostia International Physics Center (DIPC) and the Materials Physics Center in Donostia-San Sebastián (CFM) have observed for the first time, with optical methods, the quantum regime in the interaction between nano-sized spheres of gold.
The image shows, in an artistic manner, the change in color when a quantum tunnel effect is produced in a subnanometric gap.
Credit: Picture courtesy of Cambridge University
This quantum regime has been identified thanks to the change of colour of the gap or empty space between these particles when these are at distances of less than one nanometre. This work, published in Nature journal, enables literally "seeing" a quantum kiss between nanoparticles.
The gap generated between two opposing nanospheres of gold can change its colour when the distance between them is less than one nanometre, according to recent research co-directed by researchers from the DIPC and the CFM (a joint center between the CSIC [Spanish Scientific Research Council] and the UPV/EHU [the University of the Basque Country]), both based in the Basque City of Donostia-San Sebastián, and in collaboration with researchers from the Universities of Cambridge and Paris-Sud.
This work published in Nature, confirmed that electrons accumulated on the gold walls around the illuminated gap between the spheres can "jump" from one to the other, thanks to the tunnel effect, thus reducing the accumulated charge on the surface of each of these spheres and modify the colour of the gap from red to blue (blueshifting).
This work enables literally "seeing" the effects of quantum mechanics and shows how light interacts with matter at subnanometre sizes. The change in colour of the gap is a "chromatic fingerprint" that identifies the initiation of a quantum regime therein - an effect that had been predicted by the theoretical team of Dr. Aizpurua, the lead researcher in Donostia, and now fully identified as a result of this research. To this end, highly sophisticated experiments have been combined with very advanced theories.
When two metallic spheres with a sufficiently small separation between them are illuminated with white light, this gap acquires colour thanks to the interaction of the electrons on the surface of the spheres with light. The beam of light 'pushes' the electrons and makes them oscillate, which gives a red colour to the gap. As the spheres get closer, the electron charge increases and this red colour intensifies. When the distance between both is reduced to under 0.35 nanometres, this accumulation of charge can be seen to drop, due to the tunnel effect, and thanks to which the electrons can jump from one ball to another without the spheres coming into contact with each other. Just as the quantum theory developed by the research teams in Donostia and Paris predicted, it is possible to identify this quantum electronic leap, given that, as the accumulated charge drops, the red colour of the gap changes to blue.
Experimental team leader and University of Cambridge researcher, Professor Jeremy Baumberg compares this reduction in charge with the tension released from a kiss "we think of this like the tension building up between a romantic couple. As their faces get closer the tension mounts, and only a kiss discharges this energy". In this case, however, the gold nanospheres approaching each other generate a virtual kiss, as they never actually touch, releasing the charge on their surfaces and changing the colour of the gap between them. As Professor Baumberg says, "it is practically like kissing, without the lips actually touching".
The experimental team at Cambridge explained: "aligning two gold nano-particles is like closing your eyes and trying to hold two needles with the fingers of either hand so that the points of each needle touch. Achieving this has meant years of hard work".
Javier Aizpurua commented that, in order to predict the colour changes now confirmed with this experiment, "the fusion of the quantum vision with the classical vision of the world" was necessary. "The modelling of so many electrons oscillating within the gold particles in response to a beam of light could not be described with existing theories", assured the CSIC and DIPC researcher.
This new result establishes a fundamental quantum limit for the minimum dimensions within which we can trap light. Moreover, this reinterpretation of the interaction between light and matter at a sub-nanometric scale could provide new ways of describing and measuring the atomic-scale world and open doors to new strategies for the manufacture of even smaller optoelectric technological devices and access new limits of resolution in photochemistry.
This research was funded by the Basque Government through its Science Agency, Ikerbasque, and the ETORTEK Nanoscience and Nanotechnology project, as well as by a European Union initiative through the Eranet CUBiHOLE project which originally brought together the teams involved in this research. Part of this work was developed during the time spent by Professor Baumberg as an Ikerbasque Visiting Professor at the DIPC.
Aitziber Lasa | EurekAlert!
Squeezing light at the nanoscale
17.06.2018 | Harvard John A. Paulson School of Engineering and Applied Sciences
The Fraunhofer IAF is a »Landmark in the Land of Ideas«
15.06.2018 | Fraunhofer-Institut für Angewandte Festkörperphysik IAF
Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.
Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...
The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.
Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.
An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.
Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...
Light detection and control lies at the heart of many modern device applications, such as smartphone cameras. Using graphene as a light-sensitive material for...
Water molecules exist in two different forms with almost identical physical properties. For the first time, researchers have succeeded in separating the two forms to show that they can exhibit different chemical reactivities. These results were reported by researchers from the University of Basel and their colleagues in Hamburg in the scientific journal Nature Communications.
From a chemical perspective, water is a molecule in which a single oxygen atom is linked to two hydrogen atoms. It is less well known that water exists in two...
13.06.2018 | Event News
08.06.2018 | Event News
05.06.2018 | Event News
15.06.2018 | Materials Sciences
15.06.2018 | Ecology, The Environment and Conservation
15.06.2018 | Power and Electrical Engineering