David Thouless
Nobel laureate whose advances in physics were compared to the discovery that the Earth is round
DAVID THOULESS, who has died aged 84, won a half share of the 2016 Nobel Prize in Physics, with Duncan Haldane and Michael Kosterlitz sharing the other half, for what the Royal Swedish Academy of Sciences described as “theoretical discoveries of topological phase transitions and topological phases of matter”.
The research of the three Britishborn scientists related to the world of quantum mechanics, where there are no solid items and where matter – atoms and their sub-particles – are made of extremely fragile waves which can only be described by mathematical equations.
Essentially, Thouless and his fellow prize-winners found a way to explain astonishing phenomena that occur in superconductors, thin magnetic films and other unusual matter at very low temperatures and, according to the Nobel committee, created “new perspectives on the development of innovative materials”.
Their work has been described as introducing a “paradigm shift” in quantum physics akin to the discovery that the Earth is round. It opened a door to a new research field of topology and over the past 20-odd years many physicists worldwide have become involved in investigating its future possibilities. These include quantum computing, the idea being to create a new way of storing information by switching “knots” in the quantum wave on and off – similar to the way silicon-based transistors work in today’s computers.
In 2016, at the press conference announcing the award of the Nobel, Thors Hans Hansson of the prize committee, recognising that such concepts were difficult for other scientists, let alone reporters, attempted to create a visual analogy using a cinnamon bun, a bagel and a pretzel. “For us these things are different,” he explained. “One is sweet, one is salty; they are different shapes. But if you are a topologist there is only one thing that is really interesting with these things. This thing (the bun) has no holes, the bagel has one hole, the pretzel has two holes.”
He went on: “The number of holes is what the topologist would call a topological invariant. I challenge you to imagine what is half a hole. You cannot have half a hole.”
The explanation only seems to have added to the general bafflement, though The Daily Telegraph’s science
editor Sarah Knapton bravely hazarded a more lucid account: “Topology describes properties that remain intact when an object is stretched, twisted or deformed,” she wrote. “The three scientists applied it to the study of very thin layers of materials … Just as a bagel can only ever have one hole – so materials with a certain topology will only be able to conduct by a defined amount.”
David James Thouless was born on September 21 1934 at Bearsden, Scotland, and was brought up in Cambridge in an academic home. His father, Robert Thouless (1894–1984), was an eminent psychologist who coined the term “phenomenal regression” to describe the tendency for perceptions of a shape to be experienced as nearer to the shape of a related and known object than it actually is. Robert Thouless was also known for his radio programmes on critical thinking and was the author of the popular book (still in print) Straight and Crooked Thinking.
David’s mother, Ella, known as “Priscilla”, came from a family that had produced Church of England clergymen from the 17th century; Priscilla’s brother, Neville Gorton, was the Bishop of Coventry who was involved in building the new cathedral after the war. Priscilla herself won a scholarship in English Literature to Manchester University and taught English before starting a family.
From early childhood David showed unusual mathematical gifts; as a fouryear-old he once counted up to more than 1,000 in an effort to see how far counting went. The war broke out just before his fifth birthday, when David and his sister were evacuated to his grandmother’s house in Devon, where he taught himself to read and write, returning to Cambridge when it became clear that hostilities were not imminent.
Thouless went on to win the top scholarship to Winchester College, where his termly reports enthused over his progress in mathematics, but were less complimentary about his untidy presentation and handwriting.
He won a scholarship to read Natural Sciences at Trinity Hall, Cambridge, and went on to do postgraduate research under the future Nobel Prize-winner Hans Bethe, who was on sabbatical from Cornell University at Cambridge’s Cavendish Laboratory, and with whom Thouless returned to Cornell to take a PHD in Theoretical Physics. While there, he met Margaret Scrase, a biology student. They married in 1959.
While his wife completed her degree, Thouless obtained a postdoctoral fellowship for a year at the Lawrence Radiation Laboratory in Berkeley, California, and taught a course in Atomic Physics. Returning to Britain, Thouless moved to the Department of Mathematical Physics at Birmingham University for two more years of postdoctoral research, working under Professor Rudolf Peierls.
In 1961 Thouless was appointed Director of Studies in Physics and a Fellow of Churchill College, Cambridge, and became a lecturer in the department of Mathematics and Theoretical Physics. He was appointed Professor of Mathematical Physics at Birmingham in 1965, taking the Chair vacated when Rudolf Peierls moved to Oxford.
His research work really took off in the 1970s when he began a collaboration with Michael Kosterlitz, a Scottish-born postdoctoral research fellow. In a later BBC interview, Kosterlitz recalled that he had first come across Thouless at Cambridge when he attended one of his lectures, recalling him as looking like a “young kid”, albeit with a “mind operating at a different level from the rest of us”.
Their collaboration resulted in the Kosterlitz-thouless transition theory, described in a 1973 paper, “Metastability and phase transitions in two-dimensional systems”, which was one of two cited for the 2016 Nobel Prize in Physics.
By the end of the decade, however, the environment in the UK for research in theoretical physics became so unsupportive that Thouless decided to move to America. There, after a brief stint at Yale, he took up an appointment as professor of physics at the University of Washington in Seattle. In 1982, with Kohmoto, Nightingale and den Nijs, he published the second paper for which he was cited for the Nobel Prize: “Quantized Hall conductance in a two-dimensional periodic potential”.
David Thouless published two books, Quantum Mechanics of Manybody Systems (1961, now in its third edition), and Topological Quantum Numbers in Non-relativistic Physics in 1998.
He was described by colleagues as a shy, otherworldly, self-deprecating man, but one who did not suffer fools gladly and whose rather austere lifestyle and unclubbable nature probably led to recognition for his achievements coming later than it might otherwise have done.
He was elected a Fellow of the Royal Society in 1979, a Fellow of the American Academy of Arts and Sciences (1981), a Fellow of the American Physical Society (1987) and a member of the US National Academy of Sciences (1995). As well as the Nobel Prize he was awarded the 1990 Wolf Prize in physics.
Sadly, by the time he won a half share of the Nobel Prize, Thouless had succumbed to dementia, though according to one of his sons he was “delighted” with the award. Towards the end of his life, he and his wife returned to Cambridge.
Their children, two sons and a daughter, recall a kindly father who would always read them bedtime stories, Swallows and Amazons being a favourite, and would take them on family holidays, often arranged around scientific conferences, in a Bedford camper van.
Thouless’s wife and children survive him.