S S Verma
This year’s Physics Noble prize was given to the research on, “experimental methods that generate attosecond pulses of light for the study of electron dynamics in matter” and is shared equally by Pierre Agostini, Ferenc Krausz and Anne L’Huillier. Pierre Agostini (born 1941) is PhD (1968) from Aix-Marseille University, France and at present is Professor at The Ohio State University, Columbus, USA. Ferenc Krausz, born 1962 in Mór, Hungary is PhD (1991) from Vienna University of Technology, Austria and presently is Director at Max Planck Institute of Quantum Optics, Garching and Professor at Ludwig-Maximilians-Universität München, Germany. Anne L’Huillier, born 1958 in Paris, France. PhD (1986) from University Pierre and Marie Curie, Paris, France and at present is Professor at Lund University, Sweden.
The three Nobel Laureates in Physics 2023 are being recognised for their experiments, which have given humanity new tools for exploring the world of electrons inside atoms and molecules. Pierre Agostini, Ferenc Krausz and Anne L’Huillier have demonstrated a way to create extremely short pulses of light that can be used to measure the rapid processes in which electrons move or change energy. Fast-moving events flow into each other when perceived by humans, just like a film that consists of still images is perceived as continual movement. If we want to investigate really brief events, we need special technology. In the world of electrons, changes occur in a few tenths of an attosecond – an attosecond (equal to 1×10?18 of a second) is so short that there are as many in one second as there have been seconds since the birth of the universe.
The laureates’ experiments have produced pulses of light so short that they are measured in attoseconds, thus demonstrating that these pulses can be used to provide images of processes inside atoms and molecules. In 1987, Anne L’Huillier discovered that many different overtones of light arose when she transmitted infrared laser light through a noble gas. Each overtone is a light wave with a given number of cycles for each cycle in the laser light. They are caused by the laser light interacting with atoms in the gas; it gives some electrons extra energy that is then emitted as light. Anne L’Huillier has continued to explore this phenomenon, laying the ground for subsequent breakthroughs. In 2001, Pierre Agostini succeeded in producing and investigating a series of consecutive light pulses, in which each pulse lasted just 250 attoseconds. At the same time, Ferenc Krausz was working with another type of experiment, one that made it possible to isolate a single light pulse that lasted 650 attoseconds.
The laureates’ contributions have enabled the investigation of processes that are so rapid they were previously impossible to follow and can now open the door to the world of electrons. Attosecond physics gives us the opportunity to understand mechanisms that are governed by electrons. The next step will be utilising them as there are potential applications in many different areas. In electronics, for example, it is important to understand and control how electrons behave in a material. Attosecond pulses can also be used to identify different molecules, such as in medical diagnostics.
The Royal Swedish Academy of Sciences has awarded the 2023 Nobel Prize in Chemistry to Moungi G Bawendi, Louis E Brus and Alexei I Ekimov “for the discovery and synthesis of quantum dots”. Moungi G. Bawendi, born 1961 in Paris, France. PhD 1988 from University of Chicago, IL, USA is presently Professor at Massachusetts Institute of Technology (MIT), Cambridge, MA, USA. Louis E. Brus, born 1943 in Cleveland, OH, USA. PhD 1969 from Columbia University, New York, NY, USA is presently Professor at Columbia University,
New York, NY, USA. Alexei I. Ekimov, born 1945 in the former USSR, PhD 1974 from Ioffe Physical-Technical Institute, Saint Petersburg, Russia was formerly Chief Scientist at Nanocrystals Technology Inc., New York, NY, USA.
The Nobel Prize in Chemistry 2023 rewards the discovery and development of quantum dots, nanoparticles so tiny that their size determines their properties. These smallest components of nanotechnology now spread their light from televisions and LED lamps, and can also guide surgeons when they remove tumour tissue, among many other things. Everyone who studies chemistry learns that an element’s properties are governed by how many electrons it has. However, when matter shrinks to nano-dimensions quantum phenomena arise; these are governed by the size of the matter. The Nobel Laureates in Chemistry 2023 have succeeded in producing particles so small that their properties are determined by quantum phenomena. The particles, which are called quantum dots, are now of great importance in nanotechnology.
Quantum dots have many fascinating and unusual properties and importantly, they have different colours depending on their size. Physicists had long known that in theory size-dependent quantum effects could arise in nanoparticles, but at that time it was almost impossible to sculpt in nanodimensions. Therefore, few people believed that this knowledge would be put to practical use. However, in the early 1980s, Alexei Ekimov succeeded in creating size-dependent quantum effects in coloured glass. The colour came from nanoparticles of copper chloride and Ekimov demonstrated that the particle size affected the colour of the glass via quantum effects. A few years later, Louis Brus was the first scientist in the world to prove size-dependent quantum effects in particles floating freely in a fluid. In 1993, Moungi Bawendi revolutionised the chemical production of quantum dots, resulting in almost perfect particles. This high quality was necessary for them to be utilised in applications.
Quantum dots now illuminate computer monitors and television screens based on QLED technology. They also add nuance to the light of some LED lamps, and biochemists and doctors use them to map biological tissue. Quantum dots are thus bringing the greatest benefit to humankind. Researchers believe that in the future they could contribute to flexible electronics, tiny sensors, thinner solar cells and encrypted quantum communication – so we have just started exploring the potential of these tiny particles.
S S Verma