Anisotropic Scattering Caused by Apical Oxygen Vacancies in Thin Films of Overdoped High-Temperature Cuprate Superconductors

There is a hot debate on the anomalous behavior of superfluid density rho(s) in overdoped La2-xSrxCuO4 films in recent years. The linear drop of rho(s) at low temperatures implies the superconductors are clean, but the linear scaling between rho(s) (in the zero temperature limit) and the transition temperature T-c is a hallmark of the dirty limit in the Bardeen-Cooper-Schrieffer (BCS) framework [I. Bozovic et al., Nature (London) 536, 309 (2016)]. This dichotomy motivated exotic theories beyond the standard BCS theory. We show, however, that such a dichotomy can be reconciled naturally by the role of increasing anisotropic scattering caused by the apical oxygen vacancies. Furthermore, the anisotropic scattering also explains the missing Drude weight upon doping in the optical conductivity, as reported in the THz experiment [F. Mahmood et al., Phys. Rev. Lett. 122, 027003 (2019)]. Therefore, the overdoped cuprates can actually be described consistently by the d-wave BCS theory with the unique anisotropic scattering.

Automated summary

The anomalous behavior of superfluid density in overdoped La2-xSrxCuO4 films has sparked a heated debate. While the linear drop of superfluid density at low temperatures suggests clean superconductors, the linear scaling between superfluid density (in the zero temperature limit) and the transition temperature is typical of the dirty limit in the BCS framework. This dichotomy can be explained by the role of increasing anisotropic scattering caused by the apical oxygen vacancies.