DMFT Reveals the Non-Hermitian Topology and Fermi Arcs in Heavy-Fermion Systems.

Yuki Nagai,Vladyslav Kozii,Hiroki Isobe,Yang Qi,Liang Fu

doi:10.1103/physrevlett.125.227204

Abstract

When a strongly correlated system supports well-defined quasiparticles, it allows for an elegant one-body effective description within the non-Hermitian topological theory. While the microscopic many-body Hamiltonian of a closed system remains Hermitian, the one-body quasiparticle Hamiltonian is non-Hermitian due to the finite quasiparticle lifetime. We use such a non-Hermitian description in the heavy-fermion two-dimensional systems with the momentum-dependent hybridization to reveal a fascinating phenomenon which can be directly probed by the spectroscopic measurements, the bulk "Fermi arcs." Starting from a simple two-band model, we first combine the phenomenological approach with the perturbation theory to show the existence of the Fermi arcs and reveal their connection to the topological exceptional points, special points in the Brillouin zone where the Hamiltonian is nondiagonalizable. The appearance of such points necessarily requires that the electrons belonging to different orbitals have different lifetimes. This requirement is naturally satisfied in the heavy-fermion systems, where the itinerant c electrons experience much weaker interaction than the localized f electrons. We then utilize the dynamical mean field theory to numerically calculate the spectral function and confirm our findings. We show that the concept of the exceptional points in the non-Hermitian quasiparticle Hamiltonians is a powerful tool for predicting new phenomena in strongly correlated electron systems.

Highlights

We study how the non-Hermitian topology reveals itself in the two-dimensional heavy fermion compounds
Using the phenomenological approach combined with the perturbation theory, we show that the difference between the electron correlations in c and f bands naturally leads to two different lifetimes, resulting in exceptional points” (EPs) and Fermi arcs at certain temperatures
The spectral function calculated by the dynamical mean field theory (DMFT) clearly shows that there are Fermi arcs defined as the lines in the Brillouin zone where the spectral function has a peak at zero energy. We suggest that these Fermi arcs may be directly observed by angle-resolved photoemission spectroscopy (ARPES) in the small-gap Kondo lattices such as CeNiSn [18]

Summary

Introduction

DMFT Reveals the Non-Hermitian Topology and Fermi Arcs in Heavy-Fermion Systems In particular, that the presence of disorder at zero temperature [14] or interactions at finite temperature [13] generically stretchs the nodal points in two-dimensional Dirac materials into the open bulk Fermi arcs, provided the lifetimes of fermions from different orbitals are different.

Results

Conclusion