Competition between superconductivity and spin density wave

TL;DR

This paper explores the competition between superconductivity and spin density waves in the Hubbard model, revealing how different parameters influence their coexistence and providing insights into high-temperature superconductors and related phenomena.

Contribution

It introduces the effects of gap positions and parameter variations on superconductivity and SDW, offering new perspectives on high-Tc superconductor behavior.

Findings

SDW appears at higher U and certain temperature ranges

Superconductivity requires decreased U at lower temperatures

Qualitative explanation of pseudogap and superconducting states

Abstract

The Hubbard model has been investigated widely by many authors, while this work may be new in two aspects. One, we focus on the possible effects of the positions of the gaps associated with the pairing and the spin density wave. Two, we suggest that the models with different parameters are appropriate for different materials (or a material in different doped regions). This will lead to some new insights into the high temperature superconductors. It is shown that the SDW can appear at some temperature region when the on-site Coulomb interaction is larger, while the SC requires a decreased U at a lower temperature. This can qualitatively explain the relationship between superconducting and pseudogap states of Cu-based superconductors in underdoped and optimally doped regions. The superinsulator is also discussed.