Orbital-selective Kondo-lattice and enigmatic f-electrons emerging from inside the antiferromagnetic phase of a heavy fermion

TL;DR

This study reveals the coexistence of orbital-selective Kondo lattice and antiferromagnetic order in heavy fermion USb2, showing a temperature-dependent evolution of electronic states and a novel electronic transition at 45 K.

Contribution

It demonstrates the orbital selectivity of Kondo hybridization within the antiferromagnetic phase, introducing a new perspective on heavy fermion coexistence phenomena.

Findings

Visualization of a large gap in the antiferromagnetic phase at high temperatures.

Gradual development of Kondo hybridization below Tcoh 80 K.

Discovery of a first-order like electronic transition at Tstar 45 K.

Abstract

Novel electronic phenomena frequently form in heavy fermions as a consequence of the mutual nature of localization and itineracy of f electrons. On the magnetically ordered side of the heavy fermion phase diagram, f moments are expected to be localized and decoupled from the Fermi surface. It remains ambiguous whether a Kondo lattice can develop inside the magnetically ordered phase. Using spectroscopic imaging with the scanning tunneling microscope, complemented by neutron scattering, x ray absorption spectroscopy, and dynamical mean field theory, we probe the electronic states in the antiferromagnetic USb2 as a function of temperature. We visualize a large gap in the antiferromagnetic phase at high temperatures, T lower than TN 200 K, within which Kondo hybridization gradually develops below Tcoh 80 K. Our dynamical mean field theory calculations indicate the antiferromagnetism and Kondo lattice to reside predominantly on different f orbitals, promoting orbital selectivity as a new conception into how these two phenomena coexist in heavy fermions. Finally, at Tstar 45 K we discover a novel 1st order like electronic transition through the abrupt emergence of non trivial 5f electronic states that may share some resemblance to the hidden order phase of URu2Si2.