Green's Function Zeros in Fermi Surface Symmetric Mass Generation

TL;DR

This paper investigates interaction-driven Fermi surface gaps without symmetry breaking, demonstrating the presence of Green's function zeros in a bilayer fermion model through numerical and theoretical analysis.

Contribution

It provides the first detailed evidence of Green's function zeros in Fermi surface symmetric mass generation phases using combined numerical and field-theoretical approaches.

Findings

Green's function zeros are present in SMG insulators across coupling regimes.

SMG phase preserves all symmetries and has no mean-field single-particle interpretation.

Zero Fermi surface features are robust and detectable via spectroscopy.

Abstract

The Fermi surface symmetric mass generation (SMG) is an intrinsically interaction-driven mechanism that opens an excitation gap on the Fermi surface without invoking symmetry-breaking or topological order. We explore this phenomenon within a bilayer square lattice model of spin-1/2 fermions, where the system can be tuned from a metallic Fermi liquid phase to a strongly-interacting SMG insulator phase by an inter-layer spin-spin interaction. The SMG insulator preserves all symmetries and has no mean-field interpretation at the single-particle level. It is characterized by zeros in the fermion Green's function, which encapsulate the same Fermi volume in momentum space as the original Fermi surface, a feature mandated by the Luttinger theorem. Utilizing both numerical and field-theoretical methods, we provide compelling evidence for these Green's function zeros across both strong and weak coupling regimes of the SMG phase. Our findings highlight the robustness of the zero Fermi surface, which offers promising avenues for experimental identification of SMG insulators through spectroscopy experiments despite potential spectral broadening from noise or dissipation.