Within a Kondo lattice, the strong hybridization between electrons localized in real space (r-space) and those delocalized in momentum-space (k-space) generates exotic electronic states called ‘heavy fermions’. In URu2Si2 these effects begin at temperatures around 55 K but they are suddenly altered by an unidentified electronic phase transition at To = 17.5 K. Whether this is conventional ordering of the k-space states, or a change in the hybridization of the r-space states at each U atom, is unknown. Here we use spectroscopic imaging scanning tunnelling microscopy (SI-STM) to image the evolution of URu2Si2 electronic structure simultaneously in r-space and k-space. Above To, the ‘Fano lattice’ electronic structure predicted for Kondo screening of a magnetic lattice is revealed. Below To, a partial energy gap without any associated density-wave signatures emerges from this Fano lattice. Heavy-quasiparticle interference imaging within this gap reveals its cause as the rapid splitting below To of a light k-space band into two new heavy fermion bands. Thus, the URu2Si2 ‘hidden order’ state emerges directly from the Fano lattice electronic structure and exhibits characteristics, not of a conventional density wave, but of sudden alterations in both the hybridization at each U atom and the associated heavy fermion states.
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- Supplementary Information (1.8M)
This file contains Supplementary Notes (I)-(IX), Supplementary Figures S1-S9 with legends and References.
- Supplementary Video 1 (2.3M)
This movie shows the Fourier transform of the real space conductance maps of Th-doped URu2Si2 in the heavy fermion paramagnetic phase at a temperature of 19K. The patterns are due to quasiparticle interference. The red diamonds in the corners mark the locations of the U atom reciprocal lattice vectors.
- Supplementary Video 2 (4.8M)
This movie shows the Fourier transform of the real space conductance maps of Th-doped URu2Si2 in the hidden order phase at a temperature of 1.9K. The red diamonds in the corners mark the locations of the U atom reciprocal lattice vectors. The patterns are due to quasiparticle interference. The two dimensional patterns are seen to become highly separated from the patterns seen at 19K for biases -3mV to 3mV.