Condensed-matter physics pioneer and Nobel laureate Anthony Leggett dies aged 87

Anthony Leggett, a pioneering figure in condensed-matter physics and Nobel laureate, passed away on March 8 at the age of 87. His groundbreaking work on the theory of superconductors and superfluidity earned him the 2003 Nobel Prize in Physics, which he shared with Alexei Abrikosov and Vitaly Ginzburg. Born in London on March 26, 1938, Leggett initially pursued a degree in literae humaniores at the University of Oxford, focusing on classical languages, literature, philosophy, and Greco-Roman history. Despite his strong background in philosophy, he felt that the subject relied more on verbal dexterity than objective criteria, leading him to explore a career in physics.

As part of an experiment at Oxford to determine if a classics scholar with minimal scientific training could transition into a physicist, Leggett was awarded a degree in physics in 1961. He then embarked on a Doctor of Philosophy (DPhil) in physics, which he completed in 1964. Following his doctoral studies, Leggett spent time as a postdoctoral researcher at the University of Illinois Urbana-Champaign in the United States and Kyoto University in Japan. In 1967, he returned to the UK, where he spent the next 15 years at the University of Sussex.

It was during his tenure at Sussex that Leggett made his Nobel-prize-winning contributions to the theory of superfluidity—the ability of a fluid to flow without viscosity. Superfluidity in helium-4 was discovered in the 1930s, and by the 1960s, several theorists had predicted that helium-3 might also exhibit superfluid behavior. However, the two isotopes of helium present distinct challenges. Helium-4 atoms are bosons, meaning they can all condense into the same quantum ground state at sufficiently low temperatures, a critical feature of both superfluidity and superconductivity. In contrast, helium-3 atoms are fermions, and the Pauli exclusion principle prevents them from occupying the same quantum state.

To address this challenge, Leggett and other researchers developed a theoretical framework to understand how helium-3 could achieve superfluidity. This involved the formation of Cooper pairs, similar to the mechanism described by the BCS theory of superconductivity, which was developed in the mid-1950s by John Bardeen, Leon Cooper, and Robert Schrieffer. The BCS theory explains how electrons, which are also fermions, overcome the Pauli exclusion principle by pairing up and forming a coherent quantum state that allows for zero electrical resistance in superconductors.

Leggett's work on superfluidity in helium-3 not only advanced our understanding of quantum fluids but also had implications for the broader field of condensed matter physics. His research laid the foundation for further exploration into the properties of superfluids and superconductors, contributing to the development of new materials and technologies. Leggett's legacy as a physicist extends beyond his Nobel Prize-winning achievements; his innovative approach to theoretical physics and his ability to tackle complex problems have inspired generations of scientists.

Throughout his career, Leggett remained active in the scientific community, publishing numerous papers and contributing to the advancement of knowledge in condensed-matter physics. His passing marks the end of an era for those who knew him personally and professionally, but his intellectual contributions will continue to resonate in the field for years to come. Leggett's life and work serve as a testament to the power of curiosity, dedication, and perseverance in the pursuit of scientific understanding.