Amplified entanglement witnessed in a quantum critical metal

How to use entanglement to elucidate quantum materials and how to identify such systems for amplified entanglement are some of the outstanding issues in the quantum information era. Here we focus on strange metals that arise in quantum critical heavy fermions [1]. At the magnetic quantum critical point, the charge degrees of freedom also exhibit singular behavior [2], suggesting a charge-spin entangled quantum critical fluid. This motivates us to use quantum information means to characterize the strange metal state. We analyze both mutual information and entanglement witness across the Kondo destruction quantum critical point [3]. The quantum Fisher information reveals multipartite entanglement in the quantum critical fluid. Our results are supported by experiments [3,4]. We also discuss the entanglement witness in electronic systems with nonlocal operators. Our work provides an entanglement characterization for the loss of quasiparticles in quantum critical metals.

[1] H. Hu et al, Nat. Phys. in press (2024); Q. Si et al, Nature 413, 804 (2001).

[2] A. Cai et al., PRL 124, 027205 (2020); L. Prochaska et al., Science 367, 285 (2020).

[3] Y. Fang et al., arXiv:2402.18552.

[4] F. Mazza et al., arXiv:2403.12779.