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Frédéric Mila wins the Charpak-Ritz Award 2024

The Charpak-Ritz Prize 2024 is awarded to Frédéric Mila for his contributions to the theory of strongly correlated systems, in particular for the successful analysis of several experimental results in systems ranging from high-temperature superconducting cuprates to frustrated quantum magnets thanks to a thorough investigation of various strongly correlated models and to a close collaboration with experimental groups.


Frédéric Mila
Immagine: SPS

Frédéric Mila is a condensed matter theory professor who taught at the University of Lausanne from 2000 to 2003 and since then at the EPFL and is widely considered a leading figure in the field of frustrated magnetism. His work is often in lose synergy with leading-edge experiments – either being inspired by experimental results or predicting phenomena motivating new experiments. Thanks to extensive collaborations with experimental groups in France, Switzerland, Japan and the US, he has contributed to the identification and explanation of several new quantum phases in magnetic models and materials and more recently also in cold atom quantum simulators. His remarkable achievements have not only advanced our understanding of complex materials but also fostered close collaborations with experimental groups, enhancing the bridge between theoretical and experimental physics.

One cornerstone of his achievements is a remarkable series of contributions to understanding a paradigmatic model of frustrated quantum magnetism known as the Shastry-Sutherland model, and the properties of the compound SrCu2(BO3)2, which is a physical realization of this fundamental model. This led to the of discovery of new quantum phases such as fractional magnetization plateaus, spin-supersolid phases, and a spin-nematic phase that can be seen as a condensate of bosonic Cooper pairs. He also showed that there is a critical point in the phase diagram of this compound under pressure that is a quantum magnetic analogue to the critical point of water.

Beyond that specific system, he has made pioneering contributions to the magnetic properties of Mott insulators. He has worked on this topic throughout his whole career, first as a post-doc (Rutgers and Neuchâtel), then as a chargé de recherche at CNRS in Toulouse, and later in Lausanne. He came up with a microscopic theory of the low-lying singlets of the kagome spin-1/2 Heisenberg model, supporting the scenario of a resonating-valence bond (RVB) ground state in that system. He also showed that the spin-1/2 ladder has a 1/2-magnetisation plateau if the inter-dimer coupling is frustrated, opening the way to the experimental investigation of magnetization plateaus in Mott insulators such as SrCu2(BO3)2.

He has also extensively worked on Mott insulators with orbital degeneracy, in particular on their connection with lattice SU(N) models. Over the years, he has contributed to the development of several theoretical approaches to investigate these models including tensor-network simulations, which led to the first concrete example of a spin-orbital algebraic quantum liquid for the SU(4) model on the honeycomb lattice, symmetry-based formulations in terms of Young tableaux that opened the way to the investigation of these models for large values of N, and a field-theory approach in 1D which led, in collaboration with a colleague from Canada, Ian Affleck, to a generalisation of Haldane’s conjecture to SU(3).

More recently he got interested in quantum simulators realised with Rydberg atoms and came up with strong evidence in favour of an unconventional chiral transition first predicted four decades ago by Huse and Fisher in the context of adsorbed layers, and with a road map towards its detection in Rydberg chains through precise measurements of the Kibble-Zurek exponent across the transition.

In addition to his research achievements, Frédéric Mila has largely contributed to the broader scientific community. In 2005, he took part in the creation of the “Highly Frustrated Magnet” program of the European Science Foundation and sat on its steering committee until 2011. In 2007, he organised a summer school and workshop on Highly Frustrated Magnets at ICTP Trieste. In 2011, with two French colleagues, he co-edited the reference book on Highly Frustrated Magnets (Springer).

Finally, I would like to mention one of his first achievements, obtained as a postdoc at ETH Zürich in collaboration with Maurice Rice, where he developed a model of the hyperfine coupling between the spins located at the copper site and the neighbouring oxygen ions in high-temperature superconducting cuprates. This model led to predictions that were shortly after confirmed by NMR experiments done in the group of Charles Slichter, a result that landed direct support to the one-band description of these materials, and to the role of magnetic fluctuations.

The SPS Board congratulates Frédéric Mila for these impressive achievements and bright career.

Teresa Montaruli