Kondo breakdown induced by the non-Hermitian complex hybridization

TL;DR

This paper investigates how non-Hermitian complex hybridization in an Anderson impurity model leads to Kondo breakdown, using both mean-field theory and exact Bethe ansatz solutions to understand the phenomenon.

Contribution

It introduces a simplified non-Hermitian Anderson impurity model with complex hybridization and provides analytical and exact solutions to explain Kondo breakdown.

Findings

Slave-boson mean-field theory explains Kondo breakdown with a complex parameter.

Bethe ansatz solutions support the mean-field results.

Non-Hermitian Green functions lose analyticity at Kondo breakdown.

Abstract

Recently, a non-Hermitian Anderson impurity model with one-body loss has been studied in [Phys. Rev. B 111, 125157 (2025)}], and it has been demonstrated that the renormalization effect generated by strong correlations counterintuitively changes the nature of dissipation into an emergent many-body dissipation that causes a Kondo breakdown. In a closely related context, it is also known that two-body loss in a non-Hermitian Kondo model triggers the Kondo breakdown. To elucidate the essence of these phenomena, we study the Anderson impurity model with a non-Hermitian complex hybridization as an effective model that provides a simple understanding of the Kondo breakdown. Using the slave-boson mean-field theory, we show that this model can explain the Kondo breakdown with a single complex parameter. Furthermore, we provide the exact Bethe ansatz solutions that support the results obtained by the slave-boson mean-field theory. Finally, we point out that the Lehmann representation for the non-Hermitian Green function cannot be obtained by the analytic continuation to the complex energy upon the Kondo breakdown, where the analyticity of the non-Hermitian Green function in the half-complex-$\omega$ plane no longer holds.