A polarized electronic Raman scattering study reveals the emergence of symmetry dependence in the electronic Raman response of single-crystalline ${\mathrm{URu}}_2{\mathrm{Si}}_2$ below the Kondo crossover scale $T_K\sim$ 100 K. In particular, the development of a coherent Kondo pseudogap predominantly in the $E_g$ channel highlights strong anisotropy in the Kondo physics in ${\mathrm{URu}}_2{\mathrm{Si}}_2$ that was previously neglected in theoretical models of this system and more generally has been sparsely treated for Kondo systems. 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 pseudogap. This generally overlooked property may have important consequences on the formation of the subsequent phases of this system, namely, the hidden order and the superconductivity.

• Received 3 May 2018
• Revised 18 April 2020
• Accepted 12 May 2020

DOI:https://doi.org/10.1103/PhysRevB.101.245103