Visualizing the Formation of the Kondo Lattice and the Hidden Order in URu2Si2

TL;DR

This study uses atomic-scale STM imaging and spectroscopy to explore the electronic states in URu2Si2, revealing how the Kondo lattice forms and how hidden order emerges through spatially modulated electronic gaps and correlations.

Contribution

It provides direct atomic-scale evidence of the spatial modulation of Kondo resonance and hidden order gap in URu2Si2, linking the two phenomena to the same electronic states.

Findings

Spatially modulated Kondo-Fano resonance observed.

Development of a bias-asymmetric energy gap in hidden order phase.

Correlation between the Kondo resonance and hidden order gap.

Abstract

Heavy electronic states originating from the f atomic orbitals underlie a rich variety of quantum phases of matter. We use atomic scale imaging and spectroscopy with the scanning tunneling microscope (STM) to examine the novel electronic states that emerge from the uranium f states in URu2Si2. We find that as the temperature is lowered, partial screening of the f electrons' spins gives rise to a spatially modulated Kondo-Fano resonance that is maximal between the surface U atoms. At T=17.5 K, URu2Si2 is known to undergo a 2nd order phase transition from the Kondo lattice state into a phase with a hidden order parameter. From tunneling spectroscopy, we identify a spatially modulated, bias-asymmetric energy gap with a mean-field temperature dependence that develops in the hidden order state. Spectroscopic imaging further reveals a spatial correlation between the hidden order gap and the Kondo resonance, suggesting that the two phenomena involve the same electronic states.