Anisotropic Kondo pseudo-gap in URu2Si2

TL;DR

This study uncovers strong anisotropy in the Kondo pseudo-gap of URu2Si2, revealing a d-wave-like symmetry dependence in the electronic response that varies across the hidden order transition.

Contribution

It demonstrates the emergence of a symmetry-dependent Kondo pseudo-gap in URu2Si2, highlighting anisotropic effects neglected in previous models and suggesting a d-wave-like gap structure.

Findings

Pseudo-gap develops predominantly in the E_g channel

Pseudo-gap magnitude increases below the hidden order transition

Pseudo-gap exhibits a d-wave-like symmetry pattern

Abstract

A polarized electronic Raman scattering study reveals the emergence of symmetry dependence in the electronic Raman response of single crystalline URu$_{2}$Si$_{2}$ below the Kondo crossover scale $T_K\sim100K$. In particular, the development of a coherent Kondo pseudo-gap predominantly in the E$_g$ channel highlights strong anisotropy in the Kondo physics in URu$_{2}$Si$_{2}$ that has previously been neglected in theoretical models of this system. A calculation of the Raman vertices demonstrates that the strongest Raman vertex does indeed develop within the E$_g$ channel for interband transitions and reaches a maximum along the diagonals of the Brillouin zone, implying a d-wave-like geometry for the Kondo pseudo-gap. Below the hidden order phase transition at $T_{HO}= 17.5K$, the magnitude of the pseudo-gap is found to be enhanced. Moreover, the anisotropy of the pseudo-gap is similar in form to that proposed for the chiral d-wave (E$_g$) superconducting state that appears below $T_c=1.5K$.