Formation of the coherent heavy fermion liquid at the hidden order transition in URu₂Si₂

Shouvik Chatterjee, Jan Trinckauf, Torben Hänke, Daniel E. Shai, John W. Harter, Travis J. Williams, Graeme M. Luke, Kyle M. Shen, and Jochen Geck

Accepted Thursday Apr 4, 2013

We present high-resolution angle-resolved photoemission spectra of the heavy-fermion superconductor . Detailed measurements as a function of both photon energy and temperature allow us to disentangle a variety of spectral features, revealing the evolution of the low-energy electronic structure across the `hidden order' transition. Already above the transition our measurements directly reveal the existence of weakly dispersive states below the Fermi level that exhibit a large scattering rate, and which do not appear to shift from above to below the Fermi level, as previously reported. Upon entering the `hidden order' phase these states rapidly hybridize with light conduction band states and transform into a coherent heavy fermion liquid, coincident with a dramatic drop in the scattering rate. This evolution is in stark contrast with the gradual crossover expected in Kondo lattice systems, which we attribute to the coupling of the heavy fermion states to the `hidden order' parameter.