Oxygen Isotope Effect Study of (Y, Pr)Ba₂Cu₃O_7-δ Thin Films

For cuprate superconductors, oxygen isotope effect (OIE) has been used to probe the extent of electron-phonon interactions in the pairing mechanism [1] and in the pseudogap formation [2]. In this talk, we present a new OIE study of Pr-doped YBa₂Cu₃O_7-δ (YPBCO), which is the only member of the RBCO (R = rare earth) family where the superconductivity can be suppressed by doping without changing the oxygen content. To maximize doping and isotope homogeneity, epitaxial YPBCO thin films grown by pulsed laser deposition are used. The substitution of ¹⁶O by ¹⁸O is done by gas-phase diffusion and confirmed using Raman spectroscopy. Electrical transport measurements are then used to determine both the superconducting critical temperature T_c and the pseudogap onset temperature T*, to look for correlations between the isotope shifts of T_c and of T*. Our results are discussed in light of past and recent studies of the pseudogap [2, 3], and in connection with the charge order that is ubiquitouly seen in underdoped cuprates [4].

[1] G. Zhao et. al., PRB 51 16487(R) (1995)

[2] D. Temperano etl., PRL 84 1990 (1999)

[3] L. Zhao et. al., Nat. Phys. 13 250 (2017)

[4] R. Comin et. al., Annu. Rev. Con. Mat. Phys. 7 369 (2016)