Thickness dependence of superfluid density scaling in DyBa2Cu3O7-x thin films

Synopsis

Understanding the nature of the pseudogap phase and the relationship between charge order and superconductivity in the cuprates remains an outstanding challenge [1]. Recently, 2D superconductivity has gained much interest due to its discovery in a variety of unconventional materials, and advancements in MBE growth of thin films have shown that 2D superconductivity can also exist in the cuprates [2]. One interesting approach, therefore, is to investigate the evolution of cuprate physics-archive in the ultra-thin film limit where only a few superconducting CuO₂ planes are present. In this talk I will discuss recent measurements of the temperature dependence of the superfluid density as a function of thickness as well as measurements of the terahertz and infrared optical conductivity in a series of superconducting DyBa₂Cu₃O_7-x thin films. We find that in the ultra-thin film limit the temperature scaling rapidly approaches that expected for dirty s-wave superconductivity, while with decreasing oxygen content the scaling shows the opposite trend. These results suggest an increasing isotropic order parameter component below a threshold thickness due to distortions of the Fermi surface in the 2D limit.

[1] B. Keimer et. al., Nature 518, 179–186.

[2] G. Logvenov et. al., Science 326, 5953, 699—702.