Superconductivity in La(1.56)Sr(0.44)CuO(4)/La(2)CuO(4) superlattices

TL;DR

This study reveals that La(1.56)Sr(0.44)CuO(4)/La(2)CuO(4) superlattices exhibit superconductivity with a transition temperature around 25 K, characterized by highly anisotropic, sheet-like superconducting behavior confirmed through muSR measurements.

Contribution

The paper demonstrates superconductivity in non-superconducting layered superlattices and provides insights into its anisotropic nature and underlying mechanisms using muSR techniques.

Findings

Superlattices show superconductivity at T_c ≈ 25 K.

Superconductivity is highly anisotropic and sheet-like.

Vortex interactions are dominated by electromagnetic coupling.

Abstract

Superlattices of the repeated structure La(1.56)Sr(0.44)CuO(4)/La(2)CuO(4) (LSCO-LCO), where none of the constituents is superconducting, show a superconducting transition of T_c \simeq 25 K. In order to elucidate the nature of the superconducting state we have performed a low-energy muSR study. By applying a magnetic field parallel (Meissner state) and perpendicular (vortex state) to the film planes, we could show that superconductivity is sheet like, resulting in a very anisotropic superconducting state. This result is consistent with a simple charge-transfer model, which takes into account the layered structure and the difference in the chemical potential between LCO and LSCO, as well as Sr interdiffusion. Using a pancake-vortex model we could estimate a strict upper limit of the London penetration depth to 380 nm in these superlattices. The temperature dependence of the muon depolarization rate in field cooling experiments is very similar to what is observed in intercalated BSCCO and suggests that vortex-vortex interaction is dominated by electromagnetic coupling but negligible Josephson interaction.