Isotope effect in the presence of a pseudogap

TL;DR

This paper explores how the pseudogap phenomenon in underdoped high-Tc superconductors influences the isotope effect, revealing that the pseudogap generally enhances the isotope exponent, aligning with experimental observations.

Contribution

It demonstrates that the pseudogap phenomenon significantly increases the isotope exponent, providing a theoretical explanation consistent with experimental data in underdoped high-Tc superconductors.

Findings

Pseudogap strongly increases the isotope exponent.

Result is stable against strong-coupling self-energy corrections.

Enhancement holds in spin-fluctuation exchange models with weak electron-phonon coupling.

Abstract

We investigate the question whether the unusual doping dependence of the isotope exponent observed in underdoped high-Tc superconductors might be related to another unusual phenomenon observed in these systems: the pseudogap phenomenon. Within different approximations we study the influence of a phenomenological pseudogap on the isotope exponent and find that it generally strongly increases the isotope exponent, in qualitative agreement with experiments on underdoped high-Tc compounds. This result is stable against strong-coupling self-energy corrections and also holds for recently proposed spinfluctuation exchange models, if a weak additional electron-phonon coupling is considered.