Electronic structure of the hidden-order transition in URu2Si2

DIPC Seminars

Andres Santander-Syro, Université Paris-Sud, France
Donostia International Physics Center
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Electronic structure of the hidden-order transition in URu2Si2 Due to their exceptionally strong correlations, f-electron systems present a wide realm of original phase transitions and often poorly understood states of matter. One of the most intriguing is the so-called hidden-order (HO) state forming below THO =17.5 K in URu2Si2. Extensive macroscopic characterizations gathered during the last 30 years show a reduction of almost 60% in the electronic specific heat across the transition, and suggest that a gap of about 10 meV opens over more than a half of its Fermi surface. However, the identification of the associated broken symmetry and gap structure are still a riddle [1-3]. Following our observation of a Fermi-surface instability occurring at the hidden-order transition in URu2Si2 [4], we recently studied, using state-of- the art angle-resolved photoemission spectroscopy, the associated changes in its electronic structure [8, 9]. I will show how these data provide a unified microscopic picture of the large entropy loss, gap opening and Fermi-surface reconstruction inferred from thermodynamic and magneto-transport measurements in URu2Si2. I will also describe our recent studies of a quantum-critical transitions in doped URu2Si2, leading to disappearance of the hidden-order state and the onset of long-range antiferromagnetism. [1] T. M. Palstra et al. Superconducting and magnetic transitions in the heavy-fermion system URu2Si2. Phys Rev Lett. 55, 2727-2730 (1985). [2] M. B. Maple et al. Partially gapped Fermi surface in the heavy-electron superconductor URu2Si2. Phys. Rev. Lett. 56, 185-188 (1986). [3] J. A. Mydosh and P. M. Oppeneer. Colloquium: Hidden order, superconductivity, and magnetism: The unsolved case of URu2Si2. Rev. Mod. Phys. 83, 1301 (2011). [4] A. F. Santander-Syro et al. Fermi-surface instability at the ’hidden- order’ transition of URu2Si2. Nature Phys. 5, 637-641 (2009). [5] F. L. Boariu et al. Momentum-resolved evolution of the Kondo lattice into “hidden-order” in URu2Si2. Phys. Rev. Lett. 110, 156404 (2013). [6] C. Bareille et al. Momentum-resolved “hidden-order” gap structure, symmetries, and entropy loss in URu2Si2. Nature Commun. 5, 4326 (2014). Host: Enrique Ortega