From Dynamical Charge Scaling to Quantum Entanglement 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]. At the Kondo destruction QCP, we find both the charge and spin channels to be critical and obey E/T scaling. Our results provide a natural understanding of the dynamical scaling recently discovered in the charge responses at the antiferromagnetic QCP of the compound YbRh2Si2 [4]. The theoretical results are connected to the singular charge response seen in a dynamical large-N calculation of a Bose-Fermi Kondo model [5], and are understood in terms of an f-electron delocalization-localization transition [4]. We further elucidate this mechanism using the concept of dynamical Kondo effect, which we demonstrate by calculating the entanglement entropy and mutual information across the Kondo-destruction QCP [3].

[1] S. Paschen & Q. Si, Nat. Rev. Phys. (arXiv:2009.03602); S. Kirchner et al, Rev. Mod. Phys. 92, 011002 (2020); Q. Si et al, Nature 413, 804 (2001); P. Coleman et al, J. Phys. Conden Matter 13, R723 (2001).
[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. Prochaska et al, Science 367, 285 (2020).
[5] L. J. Zhu, S. Kirchner, Q. Si, A. Georges, Phys. Rev. Lett. 93, 267201 (2004).