Author: ["Andrés F. Santander-Syro","Markus Klein","Florin L. Boariu","Andreas Nuber","Pascal Lejay","Friedrich Reinert"]
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Abstract
URu2Si2 is full of mystery. Despite having f-electrons, it is unclear whether heavy electrons are present in the ‘hidden order’ phase. Thanks to photoemission studies, itinerant heavy electrons have been observed just above the hidden-order phase transition, below which the electronic energy spectrum develops a gap. Solids with strong electron correlations generally develop exotic phases of electron matter at low temperatures1,2,3. Among such systems, the heavy-fermion semimetal URu2Si2 exhibits an enigmatic transition at To=17.5 K to a ‘hidden-order’ state for which the order parameter remains unknown after 23 years of intense research4,5. Various experiments point to the reconstruction and partial gapping of the Fermi surface when the hidden order establishes6,7,8,9,10,11,12,13,14. However, up to now, the question of how this transition affects the electronic states at the Fermi surface has not been directly addressed by a spectroscopic probe. Here we show, using angle-resolved photoemission spectroscopy, that a band of heavy quasiparticles drops below the Fermi level on the transition to the hidden-order state. Our data provide the first direct evidence of a large reorganization of the electronic structure across the Fermi surface of URu2Si2 occurring during this transition, and unveil a new kind of Fermi-surface instability in correlated electron systems.Cite this article
Santander-Syro, A., Klein, M., Boariu, F. et al. Fermi-surface instability at the ‘hidden-order’ transition of URu2Si2. Nature Phys 5, 637–641 (2009). https://doi.org/10.1038/nphys1361 