Fermi surface symmetric mass generation: a quantum Monte-Carlo study

TL;DR

This study uses quantum Monte-Carlo simulations to explore a bilayer fermionic model exhibiting Fermi surface symmetric mass generation, revealing a phase transition and spectral features relevant to high-$T_c$ superconductors.

Contribution

It provides the first unbiased quantum Monte-Carlo analysis of Fermi surface SMG in a bilayer model, identifying the phase transition and spectral characteristics.

Findings

Identified a quantum phase transition from exciton insulator to SMG phase.

Spectral function shows a flat dispersion with broadening in the SMG phase.

Zero-frequency Green's function zeros form a surface at the original Fermi surface.

Abstract

The symmetric mass generation (SMG) phase is an insulator in which a single-particle gap is intrinsically opened by the interaction, without involving symmetry spontaneously breaking or topological order. Here, we perform unbiased quantum Monte-Carlo simulation and systematically investigate a bilayer fermionic model hosting Fermi surface SMG in the strongly interacting regime. With increasing interaction strength, the model undergoes a quantum phase transition from an exciton insulator to an SMG phase, belonging to the (2+1)-dimensional O(4) universality class. We access the spectral properties of the SMG phase, resembling a Mott insulating phase with relatively flat dispersion and pronounced spectral broadening. The dispersion of Green's function zeros is extracted from spectral function, featuring a surface at zero frequency precisely located at the original non-interacting Fermi surface, which constitutes a hallmark of the Fermi surface SMG phase. The bilayer model we study is potentially relevant to the newly discovered high-$T_c$ superconductor $\rm{La}_3 \rm{Ni}_2 \rm{O}_7$. Our results in SMG phase qualitatively capture the salient features of spectral function unveiled in recent ARPES experiments, shedding new insight on the underlying physics of $\rm{La}_3 \rm{Ni}_2 \rm{O}_7$.