Obituary: David Thouless, Scottish scientist who won the Nobel prize for physics

Died: April 6, 2019

BEARSDEN-born David Thouless, who has died aged 84, had just turned 82 when he shared the 2016 Nobel Prize in Physics for his part in “theoretical discoveries of topological phase transitions and topological phases of matter.” That may be too much for the vast majority of us to get our heads round but fellow scientists said Dr Thouless’s research helped create a “paradigm shift in quantum physics” comparable to the ancient Greeks’ first suggestion that the Earth may not be flat, but round.

Announcing the award in October 2016, the Nobel prize committee tried to explain their citation to bewildered journalists – and even many scientists – by producing a cinnamon bun, a bagel and a pretzel as visual props.

"For us, these things are different," said Thors Hans Hansson of the prize committee. "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. "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."

Still a bit complex for most of us, but Dr Thouless’s research was essentially related to quantum mechanics. He blended physics, mathematics and topology to explore the nature of matter – atoms and their sub-particles – in a way that now, many years on from his early research, is applicable to quantum computing and electronics. He used mathematics to explain how “strange matter,” including superconductors and thin magnetic films, react to extremely low temperatures. He used topology to study how the continuous change in the shape or size of figures do not affect geometrical properties or spacial relations.

Mr Thouless was awarded half the 2016 Physics Prize. The other half was shared, with the same citation, by Aberdeen-born physicist Michael Kosterlitz and London-born Duncan Haldane, although both the latter pursued most of their research in the US. Dr Thouless himself spent part of his career in US academia, notably at Cornell University, New York, at the University of Berkeley, California, at Yale and latterly at the University of Washington in Seattle.

David James Thouless was born in Bearsden on September 21, 1934, but moved to Cambridge with his father Robert, an eminent psychologist, and his mother Priscilla when he was a child. His father Robert wrote the book Straight and Crooked Thinking, which is still a popular academic text book, teaching students how to analyse flawed arguments. It remains popular in US college classes where it is titled How to Think Straight.

David’s uncle Neville Gorton, the Bishop of Coventry, was involved in rebuilding Coventry Cathedral, destroyed by the Lufwaffe blitz on November 14, 1940. David was only four years old when his parents heard him count out loud from one to 1,000, stopping only when he realized there were no new numbers to count. They also recalled him, in his late teens, playing chess with a friend without a board or pieces. They spoke their moves to each other and knew in their heads where each piece was.

Having been evacuated to Devon during the war, he returned to continue his education at Winchester College, a historic public school in Hampshire, before going up to Cambridge University to read natural sciences at Trinity Hall, completing a Ph.D in theoretical physics at Cornell University in Ithaca, New York. It was there he met Margaret Scrase, a biology student whom he married in 1959.

After returning to the UK, Dr Thouless taught and researched at Churchill College, Cambridge, before being appointed Professor of Mathematical Physics at Birmingham University in 1965.

It was at Cambridge University that the young Aberdeen-born Kosterlitz attended a lecture by Dr Thouless. Teacher and pupil clicked and together they collaborated on what became known as the Kosterlitz-Thouless transition theory. It was typical of the quiet, retiring Thouless to put his name second on the 1973 paper, which was titled “Metastability and phase transitions in two-dimensional systems.” More than 40 years later, the paper was cited by the Nobel prize committee during the 2016 awards ceremony.

The other Thouless research paper cited by the committee was one Dr Thouless co-wrote in the 1980s while professor of physics at the University of Washington, Seattle. It was titled "Quantized Hall conductance in a two-dimensional periodic potential". Again, words way above the head of most of us, but finally seen as Nobel-worthy during the last years of Dr Thouless’s life. He also published two books still regarded as must-reads by students in his field: Quantum Mechanics of Many-Body Systems (1961) and Topological Quantum Numbers in Non-Relativistic Physics (1998).

As well as being a Nobel Prize winner, Dr Thouless was a Fellow of the Royal Society, a Fellow of the American Academy of Arts and Sciences, a Fellow of the American Physical Society and a member of the US National Academy of Sciences.

Although he had been suffering from dementia when awarded the Nobel, his family said he was aware and delighted when they told him. He died in Cambridge and is survived by his wife Margaret and children Michael, Christopher and Helen.

PHIL DAVISON