Superconductivity in the 2D Hubbard model: Electron doping is different

TL;DR

This study uses variational Monte Carlo to explore superconductivity in the 2D Hubbard model, revealing differences between electron and hole doping and aligning with experimental cuprate data.

Contribution

It demonstrates that superconductivity's nature and energy drivers differ between electron and hole doping in the 2D Hubbard model, with implications for understanding cuprates.

Findings

Superconductivity occurs when the Fermi surface crosses the magnetic zone boundary.

Condensate energy is larger for hole doping than for electron doping.

Superconductivity is kinetic energy driven for hole doping and potential energy driven for electron doping.

Abstract

A variational Monte Carlo calculation is used for studying the ground state of the two-dimensional Hubbard model, including hopping between both nearest and next-nearest neighbor sites. Superconductivity with d-wave symmetry is found to be restricted to densities where the Fermi surface crosses the magnetic zone boundary. The condensate energy is much larger for hole doping than for electron doping. Superconductivity is kinetic energy driven for hole doping, but potential energy driven for electron doping. Our findings agree surprisingly well with experimental data for layered cuprates, both for electron- and hole-doped materials.