top of page

Hidden Order, Superconductivity and Magnetism in URu2Si2 (5266)

November 04, 2013 – November 08, 2013


Leiden, Netherlands

Photo Credits:,,


John Mydosh, Leiden University
Jaan Zaanen, Leiden University
Peter M. Oppeneer, Uppsala University
Yuji Matsuda, Kyoto University


Superconductivity and magnetism have long been the driving forces in condensed matter physics. This is especially true for the strongly correlated electron materials (SCEM) that have produced intriguing quantum matter for the past 30 or more years. Among the collection of SCEM the metallic “heavy fermion” (HF) systems have been the source of unconventional superconductivity and novel magnetism, and continuing even today with the non-understood “non-Fermi liquids”, complex multipolar order, and exotic quantum phase transitions. Intense current interest continues using HF as model transition-metal, lanthanide and actinide-based materials for probing the above physics. Since theory is lagging far behind the experimental progress, it is essential to confront and develop theory according to experimental constraints using as many direct comparisons as possible. This is especially true with the new cutting-edge techniques (e.g., ARPES, STM/STS, REXS/RXES,  etc.)  now available on a myriad of novel SCEM.  And such is the leitmotif of this Workshop. Are radically new theories needed to describe quantum matter?

As the Rosetta Stone to HF quantum matter, one special uranium-based intermetallic compound has added fresh emerging behavior to this class of SCEM. Here we have the hidden order (HO) mystery of URu2Si2 that displays a puzzling, dramatic, non-magnetic, non-structural phase transition at 17K, which eventually becomes an unconventional superconductor at 1.5K. Yet small pressures or even lattice stress causes the emergence of strange antiferromagnetism . The symmetry breaking of the HO transition and its order parameter are unknown despite 28 years of research begun in Leiden in 1985 and with presently ca. 1000 publications. Many of these works have appeared in Nature, Science, Physical Review Letters, etc., where strong controversies exist among the various schools of HO interest and the ongoing debate has reached an intense level of contention. As a result the intriguing question was posed: Is the HO generic to other types of SCEM? The conjectured answer was yes for certain oxides, e.g., Sr2Ru3O7, crystal-field driven Pr-based Skutterudites, multipolar NpO2, 1D Bose insulators, spin-orbit-coupled transition metals, etc. These SCEM will all be all considered as possibly exhibiting HO-like transitions, a second focal point of our Workshop. This naturally integrates various themes of quantum matter into a coherent framework. And so the search has been launched to confirm the generic character of HO as a key topic of this

Thrust Area

Quantum Matter

bottom of page