Site-selective oxygen isotope effect on the magnetic-field penetration depth in underdopedY0.6Pr0.4B

Abstract

We report site-selective oxygen isotope ( 16 O/ 18 O) effect ͑OIE͒ measurements on the in-plane penetration depth ab in underdoped Y 0.6 Pr 0.4 Ba 2 Cu 3 O 7Ϫ␦ , using the muon-spin rotation technique. A pronounced OIE on the transition temperature T c as well as on ab Ϫ2 (0) was observed, which mainly arises from the oxygen sites within the superconducting CuO 2 planes ͑100% within error bar͒. The values of the corresponding relative isotope shifts were found to be ⌬T c /T c ϭϪ3.7(4)% and ⌬ ab Ϫ2 (0)/ ab Ϫ2 (0)ϭϪ6.2(1.0)%. Our results imply that in this compound the phonon modes involving the movement of planar oxygen are dominantly coupled to the electrons.

The oxygen isotope effect on the in-plane penetration depth in cuprate superconductors

“…It was shown that in optimally doped YBa 2 Cu 3 O 7−δ the planar oxygen mainly (≥ 80 %) contribute to the total OIE on T c . These results were confirmed by Zhao et al [31] and later by Khasanov et al [21]. Both groups [31,21] found that in underdoped Y 1−x Pr x Ba 2 Cu 3 O 7−δ the predominant contribution (100 % within error bar) arises from the oxygen within the superconducting CuO 2 planes [see …”

“…The error bars of the "trivial" 16 O pac point (zero isotope shift by definition) indicate the intrinsic uncertainty in the determination of T c and λ ab . After [21].…”

“…Insight in this respect can be obtained from studying the site-selective OIE (SOIE) on λ ab . Khasanov et al [21] [25,24]. The site-selectivity of the oxygen exchange was checked by Raman spectroscopy [see Fig.…”

“…For a detailed description of our work we refer to Refs. [14,15,16,17,18,19,20,21,22]. In this review it is demonstrated that the muon spin rotation (µSR) technique is a very powerful and unique tool to investigate the OIE on the magnetic penetration depth in HTS.…”

Evidence for Polaron Formation in High-Temperature Superconducting Cuprates: Experiment and Theory

“…Note that-as outlined above-the theoretical data (solid line) have been obtained by renormalizing t 2 and t 4 , whereas the renormalization of t 1 (dashed line) yields the wrong doping dependence of α O . In addition to this study, also site-selective OIE investigations of Y 1 − x Pr x Ba 2 Cu 3 O 7−δ have been performed, thereby clearly revealing that the planar oxygen atoms contribute dominantly to the total OIE on T c at all doping levels, whereas the contribution of chain and apical oxygen ions is only negligible [32][33][34]. However, these findings do not imply that chain and apical oxygen ions are irrelevant to superconductivity, since their small density of states as compared to the one of the planar oxygen ions leads to a small or even vanishing contribution to the total OIE [35].…”