Results

Abstract

AbstractThe formation of Cooper pairs, a bound state of two electrons of opposite spin and momenta by exchange of a phonon, is a defining feature of conventional superconductivity. In the cuprate high temperature superconductors, even though it has been established that the superconducting state also consists of Cooper pairs, the pairing mechanism remains intensely debated. In this chapter, we investigate superconducting pairing in the Bi2Sr2CaCu2O8+δ (Bi2212) cuprate by employing spectral functions obtained directly from angle-resolved photoemission (ARPES) experiments as input to the Bethe-Salpeter gap equation. Assuming that Cooper pairing is driven solely by spin fluctuations, we construct the single-loop spin-fluctuation-mediated pairing interaction, and use it to compute the eigenfunctions and eigenvalues of the Bethe-Salpeter equation in the particle-particle channel for multiple Bi2212 samples. We find that, as the temperature is reduced, the leading eigenvalue increases upon approaching T c, reaching a value of approximately unity at the T c corresponding to each doping value. Moreover, the Bethe-Salpeter eigenfunctions, which reflect the properties the pairing interaction, have d symmetry in k-space, as observed experimentally. These results suggest that spin fluctuations are a viable candidate for the pairing “glue” in the cuprate high temperature superconductors.KeywordsARPESSpectral functionInelastic neutron scattering (INS)Spin susceptibilityRandom phase Approximation (RPA)Bethe-Salpeter equationd-Wave symmetryExchange energyCritical temperatureHubbard model