Anthony Leggett not only made a name for himself as a pioneering academic physicist but in 2003 he shared the Nobel Prize in physics for his research on superfluidity and the theory of superfluidity. However, he had left science at school as something “incomprehensible” – especially physics, which “knows in one ear and out the other” – and instead got a degree in art.
Superfluids, first observed in the early 1930s, may not be understood by many people but scientists find them of endless interest because they behave in a similar way to superconductors—materials that lose their electrical resistance when cooled below a certain temperature.
Atoms with the same number of protons but different numbers of neutrons are called isotopes. Helium has nine known isotopes but only helium-3 and helium-4 are stable, meaning they do not undergo radioactive decay. Superfluidity describes the ability of these two isotopes of liquid helium (the same gas used to fill party balloons, but in a liquid state) to flow with zero viscosity at very low temperatures, which means it can move without friction. Near absolute zero (minus 273.15C) liquid helium can flow through very small channels and up the walls of the container as a thin film, sometimes spilling over the edge. This happens because the liquid has almost no internal resistance to movement. This liquid seems to defy gravity.
Before Leggett’s research, earlier work had shown how helium-4 turned into a lot of water, but explaining how the much rarer isotope helium-3 did the same was a more difficult challenge, and for a long time, it eluded physicists. Leggett solved the mystery, explaining how helium-3 atoms interact to create this phenomenon. It was believed that only atoms, such as helium-4, with an equal number of protons, neutrons and electrons could turn into more water. Leggett explained how in helium-3 the atoms come together, behave collectively as a single particle and thus become a superfluid, like helium-4. It was a major breakthrough in low-temperature physics.
He said in an interview with the University of Illinois in 2018 that although the practical use of superfluid helium is still very limited, he argued that it will eventually arrive. Physicists today believe that superfluids will help us understand liquids, their lack of viscosity enables them to penetrate the smallest gaps, especially if we can make them work at room temperature. Similarly, they can be used in mechanical parts to reduce friction. A more unusual application may come in the areas of supercomputing and medical research.
Leggett’s work has proved useful in other fields, including the physics of elementary particles – the fundamental, undivided building blocks of the universe – and cosmology, possibly helping to explain the behavior of objects such as neutron stars. “Superfluidity is funny,” Leggett said after his Nobel citation. At first you can’t believe what you see, and when you know what’s going on, it seems like something you don’t know.
He shared the Nobel Prize with two Russian-born physicists, Alexei Abrikosov and Vitaly Ginzburg. They were studying the related phenomenon of superconductivity, which describes how at low temperatures certain metals allow electricity to pass through them without resistance. Although their work was done separately from Leggett’s, the judges considered it to be the same subject, so the 2003 Nobel was shared.
Anthony James Leggett was born in Camberwell, south London, in 1938, the first of five children, sisters Clare and Judith, and brothers Terence and Paul. His parents were teachers; his mother, Winifred (née Regan), taught mathematics, as did his father, Richard, who also taught physics and chemistry. Shortly after his birth the family moved south, to Upper Norwood, where they lived until 1950, saving some time during the Second World War when they were moved to Surrey.
Leggett attended a local Catholic primary school (he lost his Catholic faith in his mid-twenties) and after passing the 11-plus, the College of the Sacred Heart in Wimbledon, a grammar school where he excelled at chess, representing England under-16s.
In 1951, when he was 13, his father took a teaching job at Beaumont College, a public school run by Jesuit priests near Windsor, Berkshire. The family moved near Staines and as part of his father’s contract his three sons went to school free of charge.
In 1954 he won a scholarship to Balliol College, Oxford, taking his place in October 1955. Despite his parents’ interest in science, at school Leggett excelled in the classics and at Balliol he read the greats, a combination of Greek, Latin, philosophy and literature. He graduated first class in 1959 but became disillusioned with his studies, especially philosophy, and decided he wanted to work in a field where “in a sense nature can tell you whether you are right or wrong”.
It was the beginning of the Soviet space era called Sputnik I which was launched in 1957 and the USSR was about to put people on the road. The United States and its western allies were struggling to keep pace and the brightest minds were encouraged to study science and engineering, especially physics. As a result, Leggett switched from art to science and was accepted by Merton College, Oxford, to take a degree in physics. After gaining first class honors again, he became involved in advanced research on the properties of solids at Magdalen College.
He received his doctorate in 1964 and worked for a year at the University of Illinois at Urbana-Champaign (UIUC). It was there that he became interested in the proliferation of helium-3. A year at Kyoto University in Japan was followed by a year at Harvard University in Massachusetts before, in 1967, he was awarded a scholarship to the University of Sussex where he spent the next 15 years.
While at Sussex Leggett did the work that led to his Nobel nomination. A colleague recalled when he worked long hours: “We came back after one weekend, saw the sink full of coffee cups and realized he hadn’t come home.
He left Sussex in 1982, accepting a MacArthur professorship from UIUC where he spent the rest of his career. There he changed the focus of research, exploring how quantum mechanics – used to explain physics at the smallest scale – can shed light on the macroscopic, physical world as it interacts with people’s daily lives. He also studied Bose-Einstein condensates – a state of matter where atoms or subatomic particles are cooled to near zero – as well as glass properties at low temperatures, and high temperatures at high temperatures.
Although Leggett was intelligent, he was humble, unassuming and approachable. Regarding his discovery of helium-3 he said: “If I didn’t do it, someone else would.” In his Nobel speech he said that “no part of an honest study has ever been damaged, even if it seems so at the time.
In addition to the Nobel, he received many honors and awards: he was elected a fellow of the Royal Society in 1980 and, in 2004, he was awarded a knighthood for services to physics. He had British and American citizenship. After retiring in 2019 Leggett became a professor emeritus at UIUC.
He married Haruko (née Kinase), an anthropologist who also worked at UIUC, and whom he had met at Sussex, in 1973. Five years later they had a daughter, Elizabeth Asako. His wife, daughter and two sisters survived.
Those who were taught by Leggett found that he was always able to explain complex subjects concisely and clearly. Moreover, as a clear thinker, he could approach any physics issue with a philosopher’s mind. Another former student, James Sauls, now a physicist at Louisiana State University, said: “His speech was unique in its clarity and originality.”
Professor Sir Anthony Leggett FRS, physicist, was born on March 26, 1938. He died on March 8, 2026, aged 87.
#Sir #Anthony #Leggett #obituary #theoretical #physicist