Dynamical Scaling of Charge Responses at a Kondo Destruction Quantum Critical Point

An overarching question on quantum criticality is whether and how it goes beyond the Landau framework of order-parameter fluctuations. In the studies of heavy fermion metals, the notion of Kondo destruction has been developed to address this issue [1]. Microscopically, it captures how the inter-local-moment singlet formation dynamically competes with the Kondo-singlet formation at the quantum critical point (QCP). An exciting recent surprise is that charge dynamics is also singular and shows omega/T scaling at the prototype antiferromagnetic QCP of YbRh2Si2 [2]. We study prototype models for Kondo destruction QCP, and find that both the charge and spin responses are singular and obey omega/T scaling [3,4]. The criticality of the charge dynamics originates from an f-electron delocalization-localization across the Kondo destruction QCP. Broader implications of our results are discussed, both for the beyond-Landau quantum criticality in general and for the exotic excitations and unconventional superconductivity of strongly correlated metals.

[1] S. Kirchner et al, arXiv:1810.13293; Q. Si et al, Nature 413, 804 (2001).
[2] L. Prochaska et al, arXiv:1808.02296.
[3] A. Cai et al, arXiv:1902.11293.
[4] H. Hu et al, in preparation (2019).