Emergence of charge-2$e$ bosonic carriers and pseudogaps in the dynamics of residual electrons

TL;DR

This paper demonstrates how charge-2e bosonic pairs can emerge in the attractive Hubbard model, leading to non-Fermi liquid behavior and pseudogaps, providing a microscopic basis for boson-fermion mixed liquids in correlated materials.

Contribution

It shows the emergence of charge-2e bosonic carriers in the presence of residual electrons using quantum Monte Carlo simulations, linking microscopic mechanisms to non-Fermi liquid phenomena.

Findings

Charge-2e bosonic pairs emerge with residual electrons.

Electronic spectral function exhibits pseudogap behavior.

Non-Fermi liquid behavior observed above superfluid temperature.

Abstract

Emergence of charge-2$e$ bosonic carriers as tightly bound electrons presents perhaps the simplest route to understand the non-Fermi liquid behaviors widely observed in functional materials. However, such scenario is typically discarded when unbound electrons are observed near the chemical potential. Here, using attractive Hubbard model as a representative example, we demonstrate the emergence of such ''bosonic'' bound pairs in the presence of residual low-energy electrons through determinant quantum Monte Carlo computation of their propagators. Furthermore, above the superfluid temperature the electronic spectral function is found to display a typical non-Fermi liquid behavior, namely a pseudogap near the chemical potential. This study provides the microscopic foundation for scenarios of boson-fermion mixed liquid as effective descriptions for some of the strongly correlated functional materials.