The Sir Anthony Leggett Institute Honoring Excellence in Condensed Matter Physics









The Sir Anthony Leggett Institute 
Honoring Excellence in Condensed Matter Physics



A world leader in low-temperature physics, Leggett was awarded the 2003 Nobel Prize in physics for his work on superfluidity. He has also made important contributions to the theoretical foundations of quantum mechanics. He currently serves as the John D. and Catherine T. MacArthur Chair Emeritus in Physics and the chief scientist for the Institute for Condensed Matter Theory in the Physics Department. 

Sir Tony Leggett, Physics Department
Professor Sir Anthony J. Leggett

“Students and faculty alike greatly admire Tony as brilliant scientist, outstanding citizen, and a generous mentor, colleague, and friend,” said Physics Department Head Matthias Grosse Perdekamp. “The Sir Anthony Leggett Institute will continue the rigorous pursuit of scientific excellence in an open and collegial environment – the Illinois Physics tradition that Tony has shaped and made so successful.” 

The Physics Department has been a leader in condensed matter research for almost seven decades, attracting the best students and researchers in the field. Two-time Nobel laureate John Bardeen, National Medal of Science recipient Charles Slichter, and Leggett lead the list of illustrious scientists who have served on the department's faculty, and some of the most important breakthroughs in the history of condensed matter physics, such as development of the BCS theory of superconductivity and Slichter's work on nuclear magnetic resonance, happened here. By honoring Leggett’s contributions, we hope to inspire current and future scientists to continue this legacy of excellence. 

Tony Leggett: A Scientific Life

Sir Anthony J. Leggett – or Tony, as he is affectionately known around the Physics Department – was a latecomer to science. His secondary school education emphasized classics, and he earned a bachelor's degree in literae humaniores from Balliol College, University of Oxford. He considered an academic career in philosophy, but he was ultimately drawn to physics for the possibility of “being wrong for interesting and nontrivial reasons.” So he enrolled in Merton College, Oxford to pursue a second bachelor’s degree in physics.

He went on to earn a physics doctorate, studying problems related to liquid helium for his dissertation. After holding postdoctoral appointments at Illinois, Kyoto University, Harvard University, and Oxford, he accepted a faculty position at the University of Sussex. 

It was there that Tony performed his Nobel Prize-winning research from 1972 to 1973, identifying the microscopic mechanism underlying superfluidity in helium-3 shortly after the phenomenon was discovered. He recognized that it was fundamentally different from the forms of superfluidity observed to that point and used theoretical techniques previously developed for superconductivity. Both superfluidity and superconductivity are now recognized as instances of a broader low-temperature phenomenon called “fermionic condensation.” 

In 1983, Illinois Physics offered Tony the newly endowed MacArthur Chair, and he relocated. He continued to study low-temperature systems such as liquid helium and superconductors, but he also began to think about the conceptual foundations of quantum mechanics. He was particularly interested in the quantum phenomenon of superposition, in which an object apparently exists in multiple states at the same time.

Working with Anupam Garg, Tony developed a mathematical criterion – now known as the Leggett- Garg inequality – that objects existing in only one state at a given time must satisfy. Subsequent experiments have shown that quantum systems ranging from superconductors to high-energy particles fail to meet this criterion, demonstrating that they really do exist in multiple states at once. 

In addition to his 2003 Nobel Prize, Tony was knighted by Queen Elizabeth II in 2004 “for services to physics.” 

He is still an active researcher at age 85, currently studying superfluid helium under far-from-equilibrium conditions, high-temperature superconductivity, and quantum computing. 

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This story was published October 25, 2023.

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