Investigating the Physical Origin of Unconventional Low-Energy Excitations and Pseudogap Phenomena in Cuprate Superconductors

TL;DR

This paper explores the origins of low-energy excitations and pseudogap phenomena in cuprate superconductors by modeling the interplay of competing orders, superconductivity, and quantum fluctuations, aligning theoretical results with experimental observations.

Contribution

It introduces a comprehensive model combining superconductivity, competing orders, and quantum fluctuations to explain pseudogap phenomena in cuprates, providing a unified theoretical framework.

Findings

Two energy scales associated with pseudogaps identified

High-energy pseudogap likely magnetic in origin

Low-energy pseudogap linked to competing orders

Abstract

We investigate the physical origin of unconventional low-energy excitations in cuprate superconductors by considering the effect of coexisting competing orders (CO) and superconductivity (SC) and of quantum fluctuations and other bosonic modes on the low-energy charge excitation spectra. By incorporating both SC and CO in the bare Green's function and quantum phase fluctuations in the self-energy, we can consistently account for various empirical findings in both the hole- and electron-type cuprates, including the excess subgap quasiparticle density of states, ``dichotomy'' in the fluctuation-renormalized quasiparticle spectral density in momentum space, and the occurrence and magnitude of a low-energy pseudogap being dependent on the relative gap strength of CO and SC. Comparing these calculated results with experiments of ours and others, we suggest that there are two energy scales associated with the pseudogap phenomena, with the high-energy pseudogap probably of magnetic origin and the low-energy pseudogap associated with competing orders.