Novel Isotope Effects on the Pairing Pseudogap in High-$T_{c}$ Cuprates: Evidences for Polaronic Metal and Precursor BCS-Like Pairing of Large Polarons

TL;DR

This paper investigates isotope effects on the pseudogap in cuprates using a large-polaron model and BCS-like approaches, revealing large isotope effects on the pairing temperature and explaining experimental discrepancies.

Contribution

It introduces a novel large-polaron model combined with non-standard BCS approaches to explain isotope effects on the pseudogap in cuprates, aligning theory with experiments.

Findings

Large isotope effects on the pseudogap temperature $T^{}$ in cuprates.

Precursor pairing of large polarons occurs above $T_{c}$ in the intermediate-coupling regime.

Results match experimental data and clarify previous inconsistencies.

Abstract

We have studied the novel isotope effects on the pairing pseudogap in underdoped and optimally doped cuprates within the large-polaron model and two non-standard BCS-like approaches. We have shown that in the intermediate-coupling regime the precursor pairing of large polarons occurs at a mean-field temperature $T^{\ast}>T_{c}$ and the near-absent, sizable and very large oxygen and copper isotope effects on $T^{\ast}$ exist in cuprates with small and large Fermi surfaces. Our results for $T^{\ast}$, isotope shifts and exponents in slightly underdoped and optimally doped cuprates are in quantitative agreement with existing experiments and explain the discrepancy between various experiments.