From Quantum Entanglement to Dynamical Charge Scaling at a Kondo Destruction Quantum Critical Point

A prevailing question on quantum criticality is whether and how it goes beyond the Landau framework of order-parameter fluctuations. In the studies of antiferromagnetic heavy fermion metals, the notion of Kondo destruction has been developed to address this issue [1]. Microscopically, the Kondo destruction captures how the inter-local-moment singlet formation dynamically competes with the Kondo-singlet formation at the quantum critical point (QCP).
Here, we study the Kondo destruction QCP in the Kondo lattice and related models via the quantum Monte Carlo method and identify a continuous quantum phase transition [2,3]. Via calculating local entanglement entropy and mutual information, we demonstrate the dynamical Kondo effect, which produces additional charge fluctuations at the antiferromagnetic QCP. Consequently, we find both the charge and spin channels to be critical and obey E/T scaling at QCP. The results are also connected to the singular charge response seen in a dynamical large-N calculation of a Bose-Fermi Kondo model [4], and are understood in terms of an f-electron delocalization-localization transition [5]. Our results provide a natural understanding of the dynamical scaling recently discovered in the charge responses at the antiferromagnetic QCP of the compound YbRh2Si2 [5].

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[2] A. Cai, Z. Yu, H. Hu, S. Kirchner, Q. Si, Phys. Rev. Lett. 124, 027205 (2020).
[3] H. Hu, A. Cai, Q. Si, arXiv:2004.04679 (2020).
[4] L. J. Zhu, S. Kirchner, Q. Si, A. Georges, Phys. Rev. Lett. 93, 267201 (2004).
[5] L. Prochaska et al, Science 367, 285 (2020).