Strain-Induced Inhomogeneity of the Superconducting State in Strongly Underdoped La2-xSrxCuO4 Thin Films

Strategic Insights -

Research conducted at the Polish Academy of Sciences has revealed a correlation between film morphology and the homogeneity of the superconducting state in La2-xSrxCuO4 thin films. The study found that thinner films, with a thickness of around 10 nm, exhibit the smoothest surface and the highest onset of the superconducting transition temperature (Tc), but the superconducting state in these films is strongly inhomogeneous. In contrast, thicker films, with a thickness of 70-110 nm, become less smooth, but the homogeneity of the superconducting state improves dramatically. The research suggests that the strong inhomogeneity of the thinnest films results from spatial variability of unrelaxed build-in strain and an inhomogeneous distribution of carriers.

Key Takeaways:

  • Thin La2-xSrxCuO4 films with a thickness of around 10 nm exhibit the smoothest surface and the highest onset of Tc, but the superconducting state is strongly inhomogeneous.
  • Thicker films, with a thickness of 70-110 nm, become less smooth, but the homogeneity of the superconducting state improves dramatically.
  • Strong inhomogeneity of the thinnest films is likely due to spatial variability of unrelaxed build-in strain and an inhomogeneous distribution of carriers.
  • The research suggests that homogeneity cannot be inferred solely from surface morphology.
  • Partial strain relaxation occurs in thicker films, leading to improved homogeneity of the superconducting state.
  • The study utilized imaging techniques, resistance measurements, and effective medium theory (EMT) to analyze the film surface and superconducting state.
  • The research was funded by the Slovak Research and Development Agency, Polish NSC, Vedecka grantova agency MSVVaS SR a SAV (VEGA), and other organizations.

Statistics:

  • The thickness of the thinnest films studied was around 10 nm.
  • The thickness of the thicker films studied was between 70-110 nm.
  • The onset of the superconducting transition temperature (Tc) was highest in the thinnest films.
  • The homogeneity of the superconducting state improved dramatically in thicker films.
  • The spatial variability of unrelaxed build-in strain in thinnest films was a major contributing factor to their inhomogeneity.

Sources:

  • Strain-induced Inhomogeneity of the Superconducting State In Strongly Underdoped La 2- x sr x cuo 4 Thin Films. Journal of Applied Physics, 2025;138(12).
  • Journal of Applied Physics. Aip Publishing, 1305 Walt Whitman Rd, Ste 300, Melville, NY 11747-4501, USA.
  • Polish Academy of Sciences. Institute of Physics, Lotnikow 32-46, Pl-02668 Warsaw, Poland.