This year’s Nobel Prize in Physics has been awarded to three British-born scientists, David J Thouless (half the prize), F Duncan M Haldane and J Michael Kosterlitz (jointly share the other half) for their theoretical discoveries of topological phase transitions and topological phases of matter. Their work was done more than 40 years ago and all three used mathematics, especially topological concepts, to explain unusual physical effects in rare matter states such as superconductors, superfluids and thin magnetic films. David has been given a larger share because he made crucial contributions to both the advances of phase transitions and phases of matter.
Although their work was done a long time ago, many new developments based on their initial work are emerging now. Their work paves the way for designing new materials with novel properties and potential for important applications in many future technologies. Michael and David focused on the phenomena arising in so-called flat forms of matter, ie, on surfaces inside extremely thin layers that can be considered two dimensional. This contrasts with our familiar three-dimensional space. Forty years ago, Michael and David overturned the conventional theory or idea that superconductivity or superfluidity could not occur in very thin layers of materials.
Michael and David described a type of phase transition in a thin layer of extremely cold matter. At low temperatures, vortices form tightly-bound pairs, but at higher temperatures, they separate and fly in different directions. Their behaviour has some similarity to strong interaction forces between quarks and gluons. Duncan discovered how topological concepts can be applied to chains of small magnets in certain materials. He also studied matter that forms threads so thin that they are one dimensional.
The phenomena of phase transitions in such exotic systems complement the familiar phases of usual matter like changing from solid to liquid phase. By applying topology to these unusual phases of matter, they opened the door to an unknown world, where matter can assume strange states and exotic phases. Topology probes properties of space, shapes essentially assumed by matter or materials that remain unchanged under certain deforming forces.
Their pioneering theoretical work on topological phases of matter and topological phase transitions could be used in new generations of electronic and superconducting devices with potential applications in future quantum computers. Topological materials are in the frontline of research in condensed matter physics. In practical terms, we have the reshaping of common materials into ‘topological states’ that can transport energy and information on highly miniaturised scales without overheating, which is a perennial problem in a whole variety of devices including computers.
Topological concepts could be used in robust quantum devices proving superior to classical circuit elements. These design aspects can protect quantum information by giving it robustness against being destroyed by the usual noisy environments. Topological metals could be used in improved transistors. We have, for instance, topological insulators and topological defects of all kinds such as screw dislocations in crystals, solutions etc. Manipulation of these materials and their properties are likely to play a seminal role in future supercomputers, communication devices and nanotechnology.
Medicine
Yoshinori Ohsumi of Japan has won the Nobel Prize in Medicine for his pioneering work on autophagy, a process where cells ‘eat themselves’. Autophagy is recognised as a fundamental process in cell physiology and is necessary for the orderly recycling of damaged cell parts. Understanding its working in the body has crucial implications for better health and prevention of diseases.
About 60 years ago, it was first observed that a cell could destroy its own contents by wrapping them up in membranes and then transporting them to a separate recycling compartment dubbed as the lysosome. If this is indeed the mechanism, toxic substances would accumulate in the cell causing many diseases. Cells function continously by being actively involved in all bodily biological processes. The myriad of chemical reactions lead to production of waste, which has to be disposed of. The lysosome is a membrane-bound sac found in animal cells and in single-celled eukaryotes. It contains hydrolytic enzymes that degrade aged or defective cell components or material taken in by the cell from its environment such as food particles or bacteria. The earlier work of the role played by lysosome earned the Belgian biochemist Christian de Duve, the Nobel Prize in Medicine in 1974, which he shared with George Palade and Albert Claude for their contributions to understanding the inner workings of living cells.
Yoshinori, however, identified the genetic basis for autophagy. In a series of experiments, 25 years ago, Yoshinori used baker’s yeast to identify the genes essential for autophagy and then went on to explain the underlying mechanisms for autophaging in yeast and showed that similar sophisticated machinery is involved in human cells also. Mutations in the genes involved in autophagy as well as in the autophaging processes are responsible for several conditions including cancer, various neurological diseases and diabetes.
Yoshinori’s work opened up paths in understanding the importance of autophagy in many physiological processes such as how the body adapts to starvation or how it responds to infection. When the autophagic process breaks down, links have been established to varied disorders such as Parkinson’s disease, type 2 diabetes etc.
Chemistry
The 2016 Nobel Prize in Chemistry has been jointly awarded to Jean-Pierre Sauvage (France), Sir J Fraser Stoddart (Britain) and Bernard L Feringa (The Netherlands) for the design and synthesis of molecular machines. Also called nanomachines or nanobots, these machines are a thousand times thinner than a strand of human hair, and can be made to work as tiny motors, ratchets, pistons, wheel and axles etc, to generate mechanical motion in response to stimuli like light or heat. They could slip inside the human body to deliver drugs from within. For instance, applying medicines directly to cancer cells. These molecular machines can also move objects many times their size.
The prize recognises their success in mastering motion control at the molecular scale by linking molecules together to design almost everything on a tiny scale. They were inspired by proteins that naturally act as biological machines in performing millions of functions within cells. Jean-Pierre provided an early breakthrough by linking different molecules to form a chain. In 1983, he linked two ringshaped molecules. Normally, molecules are joined by strong bonds in which atoms share electrons, but in this chain they were linked by a freer mechanical bond. The second step was taken by Sir Fraser in 1991, when he threaded a molecule ring onto a thin molecular axle and made the ring move along the axle.
He developed molecular lifts, molecular muscle etc. Bernard produced the first molecular motor in 1999, making it spin in one direction. He made a nano car in 2011, a molecular chassis holding together four motors that functioned as wheels. However, he feels there is still a long way to go in this regard.
The molecular motor is presently in the same stage as the electric motor was in the 19th century with engineers then displaying cranks and wheels unaware that they would result in electric traction on a mass scale among other things. The molecular machines have plenty of future potential for development of new nanomaterials, sensors, energy storage systems etc.