Gradual emergence of superconductivity in underdoped LSCO
/ Authors
A. Ţuţueanu, M. Kamminga, T. Tejsner, H. Jacobsen, H. Hansen, M. Lăcătuşu, J. Baas, K. L. Eliasen, J. Grivel, Y. Sassa
and 36 more authors
N. Christensen, P. Steffens, M. Boehm, A. Piovano, K. Lefmann, Astrid T. Romer Nanoscience Center, Niels Bohr Institute, U. Copenhagen, Denmark, Institut Laue-Langevin, Grenoble, France, P. Institute, Laboratory for Neutron Scattering, Imaging, Villigen, Switzerland., Zernike Institute for Advanced Materials, U. Groningen, The Netherlands., Glass, Time, Imfufa, Department of Materials Science, Environment, Roskilde University, Department of Energy Conversion, Storage, T. Denmark, Kgs. Lyngby, D. O. Physics, C. U. Technology, Goteborg, Sweden., Danish Fundamental Metrology, Horsholm
/ Abstract
We present triple-axis neutron scattering studies of low-energy magnetic fluctuations in strongly underdoped La$_{2-x}$Sr$_{x}$CuO$_{4}$ with $x=0.05$, $0.06$ and $0.07$, providing quantitative evidence for a direct competition between these fluctuations and superconductivity. At dopings $x=0.06$ and $x=0.07$, three-dimensional superconductivity is found, while only a very weak signature of two-dimensional superconductivity residing in the CuO$_2$ planes is detectable for $x=0.05$. We find a surprising suppression of the low-energy fluctuations by an external magnetic field at all three dopings. This implies that the response of two-dimensional superconductivity to a magnetic field is similar to that of a bulk superconductor. Our results provide direct evidence of a very gradual onset of superconductivity in cuprates.