Energetics of superconductivity in the two dimensional Hubbard model

TL;DR

This study investigates the energy changes associated with superconductivity in the two-dimensional Hubbard model, revealing two distinct regimes with different energetic behaviors and linking them to the pseudogap boundary.

Contribution

It identifies two regimes of superconductivity with contrasting energetics and connects the crossover to the pseudogap boundary, challenging RVB-based explanations.

Findings

Weak coupling regime: superconductivity reduces potential energy, increases kinetic energy.

Strong coupling regime: superconductivity increases potential energy, decreases kinetic energy.

Crossover coincides with the pseudogap boundary, indicating an unconventional superconductivity mechanism.

Abstract

The energetics of the interplay between superconductivity and the pseudogap in high temperature superconductivity is examined using the eight-site dynamical cluster approximation to the two dimensional Hubbard model. Two regimes of superconductivity are found: a weak coupling/large doping regime in which the onset of superconductivity causes a reduction in potential energy and an increase in kinetic energy, and a strong coupling regime in which superconductivity is associated with an increase in potential energy and decrease in kinetic energy. The crossover between the two regimes is found to coincide with the boundary of the normal state pseudogap, providing further evidence of the unconventional nature of superconductivity in the pseudogap regime. However the absence, in the strongly correlated but non-superconducting state, of discernibly nonlinear response to an applied pairing field, suggests that resonating valence bond physics is not the origin of the kinetic-energy driven superconductivity.