Hidden-Fermion Representation of Self-energy in Pseudogap and Superconducting States of Two-Dimensional Hubbard Model

TL;DR

This paper introduces a simple hidden-fermion model to describe the self-energy in the pseudogap and superconducting states of the 2D Hubbard model, aiding understanding of complex electronic states.

Contribution

It presents a novel simple equation representing the low-frequency self-energy, fitting numerical data and revealing hidden fermionic states in the Hubbard model.

Findings

Self-energy well described by a simple hidden fermion model

Parameters characterizing hidden fermions determined from data

Model provides insights into pseudogap and superconducting states

Abstract

We study the frequency-dependent structure of electronic self-energy in the pseudogap and superconducting states of the two-dimensional Hubbard model. We present the self-energy calculated with the cellular dynamical mean-field theory systematically in the space of temperature, electron density, and interaction strength. We show that the low-frequency part of the self-energy is well represented by a simple equation, which describes the transitions of an electron to and from a hidden fermionic state. By fitting the numerical data with this simple equation, we determine the parameters characterizing the hidden fermion and discuss its identity. The simple expression of the self-energy offers a way to organize numerical data of this uncomprehended superconducting and pseudogap states, as well as a useful tool to analyze spectroscopic experimental results. The successful description by the simple two-component fermion model supports the idea of "dark" and "bright" fermions emerging from a bare electron as bistable excitations in doped Mott insulators.