Superconductivity and charge carrier localization in ultrathin $\mathbf{L}{\mathbf{a}}_{1.85}\mathbf{S}{\mathbf{r}}_{0.15}\mathbf{Cu}{\mathbf{O}}_4/\mathbf{L}{\mathbf{a}}_2\mathbf{Cu}{\mathbf{O}}_4$ bilayers

Abstract

$\mathrm{L}{\mathrm{a}}_{1.85}\mathrm{S}{\mathrm{r}}_{0.15}\mathrm{Cu}{\mathrm{O}}_4$/$\mathrm{L}{\mathrm{a}}_2\mathrm{Cu}{\mathrm{O}}_4$ (LSCO15/LCO) bilayers with a precisely controlled thickness of N unit cells (UCs) of the former and M UCs of the latter ([LSCO15\_N/LCO\_M]) were grown on (001)-oriented {\slao} (SLAO) substrates with pulsed laser deposition (PLD). X-ray diffraction and reciprocal space map (RSM) studies confirmed the epitaxial growth of the bilayers and showed that a [LSCO15\_2/LCO\_2] bilayer is fully strained, whereas a [LSCO15\_2/LCO\_7] bilayer is already partially relaxed. The \textit{in situ} monitoring of the growth with reflection high energy electron diffraction (RHEED) revealed that the gas environment during deposition has a surprisingly strong effect on the growth mode and thus on the amount of disorder in the first UC of LSCO15 (or the first two monolayers of LSCO15 containing one $\mathrm{Cu}{\mathrm{O}}_2$ plane each). For samples grown in pure ${\mathrm{N}}_2\mathrm{O}$ gas (growth type-B), the first LSCO15 UC next to the SLAO substrate is strongly disordered. This disorder is strongly reduced if the growth is performed in a mixture of ${\mathrm{N}}_2\mathrm{O}$ and ${\mathrm{O}}_2$ gas (growth type-A). Electric transport measurements confirmed that the first UC of LSCO15 next to the SLAO substrate is highly resistive and shows no sign of superconductivity for growth type-B, whereas it is superconducting for growth type-A. Furthermore, we found, rather surprisingly, that the conductivity of the LSCO15 UC next to the LCO capping layer strongly depends on the thickness of the latter. A LCO capping layer with 7~UCs leads to a strong localization of the charge carriers in the adjacent LSCO15 UC and suppresses superconductivity. The magneto-transport data suggest a similarity with the case of weakly hole doped LSCO single crystals that are in a so-called {"{cluster-spin-glass state}"}

References in corpus (3)

• High-temperature interface superconductivity between metallic and insulating cuprates
• Localized Superconductivity in the Quantum-Critical Region of the Disorder-Driven Superconductor-Insulator Transition in TiN Thin Films
• Superconducting transition at 38 K in insulating-overdoped La2CuO4-La1.64Sr0.36CuO4 superlattices: Evidence for interface electronic redistribution from resonant soft x-ray scattering

Cited by in corpus (3)

• Emergence of high-temperature superconductivity at the interface of two Mott insulators
• Dimensional crossovers in the Gaussian critical fluctuations above $T_c$ of two-layer and three-layer superconductors
• A scenario for the critical fluctuations near the transition of few-bilayer films of high-temperature cuprate superconductors