Small-to-large Fermi surface fluctuations in heavy fermion systems III: Crossover between Kondo destruction and SDWr quantum criticality

The notion of Kondo destruction characterizes a beyond-Landau quantum critical point, across which Fermi surface goes from “large” to “small” [1]. Here we show that, even when the quantum transition is of a fluctuating spin-density-wave order (SDW), the upper cutoff of the Landau quantum criticality, $E_cr$, is considerably smaller than the bare Kondo scale ($E_K^0$). The small $E_cr/E_K^0$ ratio captures the dynamical competition between the RKKY and Kondo interactions. We systematically demonstrate this effect in an Anderson lattice model within an EDMFT approach. Accordingly, we propose the notion of SDW$_r$ quantum criticality, in which the associated SDW order comes from renormalized heavy quasiparticle and, accordingly, a substantial dynamical range ($E_cr$, $E_K^0$) exists for Kondo-destruction quantum criticality. We discuss why several quantum critical heavy fermion metals fall into this picture. Our work provides the foundation for the recently advanced theory of heavy-fermion superconductivity [2] presented in the previous talk.

 

[1] S. Paschen & Q. Si, Nat. Rev. Phys. 3, 9 (2021); S. Kirchner et al, Rev. Mod. Phys. 92, 011002 (2020); Q. Si et al, Nature 413, 804 (2001)

 

[2] H. Hu, et al., arXiv:2109.13224 (2021)