Leon Cooper, Nobel prize-winner who explained superconductivity and also studied learning and memory

Once dubbed ‘Dr Supercool’ by a newspaper, Cooper was a bon viveur who often drove round the campus in a Chevrolet Camaro convertible

Leon Cooper, who has died aged 94, shared the 1972 Nobel Prize in Physics with his fellow Americans John Bardeen and John Schrieffer for their development of a theory, known as the Bardeen-Cooper-Schrieffer (BCS) theory, explaining the phenomenon of superconductivity; once described as “a theorist who spends a great deal of time theorizing about what it means to theorise,” he also did pioneering research in neuroscience.
Superconductivity is the ability of some materials to lose electrical resistance when cooled to very low temperatures. It was first observed by the Dutch physicist Heike Kamerlingh Onnes in 1911 in mercury chilled to a few degrees above absolute zero. Two decades later, two German scientists discovered that magnetic fields are expelled from the material when superconductivity sets in.
But no one was able to account for such phenomena. Einstein, Heisenberg, Bohr, Pauli and Felix Bloch all tried but failed.
In 1955 Cooper, a postdoctoral student working at the Institute for Advanced Study at Princeton, joined Bardeen (who would share the Physics Nobel in 1956 for his discovery of the transistor effect) and Schrieffer at the University of Illinois, where they were researching superconductivity.
Electrical resistance arises because the electrons that carry current bounce off the nuclei of the atoms, causing them to recoil and vibrate, sapping energy from the electrons. It was Cooper who discovered that electrons in a superconductor are grouped in pairs, now called Cooper pairs, and that application of an electrical voltage to the superconductor causes all the pairs to move as a single entity, constituting a current; when the voltage is removed, current continues to flow indefinitely, because the pairs encounter no opposition.
Schrieffer went on to describe the behaviour of Cooper pairs mathematically, and in December 1957 the three scientists published their “Theory of Superconductivity” in Physical Review. It was a major breakthrough which helped solve complex puzzles to do with the often odd behaviour of neutrons and protons in the atomic nucleus. 
It also helped to account for the bizarre behaviour of pulsars – small rotating stars that emit regular bursts of radio waves – after their discovery in 1963, and helped towards the development of magnetic imaging techniques in medicine.
The elder of two children, Cooper was born Leon N Kupchik (the “N” was not short for anything) on February 28 1930 to Jewish parents in the Bronx. His father Irving Kupchik, a printing typesetter originally from Belarus, then part of the Russian Empire, had, as a Menshevik, fled his homeland after the Russian Revolution. 
His mother Anna, née Zola, was originally from Poland. She died when Leon was nine and when his father remarried, he changed his name to Cooper.
Leon took a degree in physics at Columbia University in 1951, followed by a doctorate in 1954, before joining the Institute for Advanced Study at Princeton. In 1958 he was appointed professor of physics at Brown University, Providence, Rhode Island, where he turned his mind to neuroscience, becoming director of the university’s new Center for Neural Science in 1973.
In 1982, with his doctoral students, Elie Bienenstock and Paul Munro, he published “Theory for the development of neuron selectivity: orientation specificity and binocular interaction in visual cortex” in the Journal of Neuroscience. Known as the “BCM theory of synaptic plasticity”, it is regarded as foundational to neuroscience, enabling scientists to identify fundamental mechanisms behind processes of learning and memory storage in the brain.
Once described by a Providence newspaper as “Dr Supercool,” Cooper was a bon viveur who could often be seen driving round the university campus in a 1968 Chevrolet Camaro convertible.
His first marriage, to Martha Kennedy, was dissolved. He is survived by his second wife, Kay and by two daughters from his first marriage.
Leon Cooper, born February 28 1930 , died October 23 2024