Abstract
Using inelastic neutron scattering, we show that the onset of superconductivity in underdoped coincides with a crossover from well-defined spin waves to overdamped and diffusive spin excitations. This crossover occurs despite the presence of long-range stripe antiferromagnetic order for samples in a compositional range from to 0.055, and is a consequence of the shrinking spin-density wave gap and a corresponding increase in the particle-hole (Landau) damping. The latter effect is captured by a simple itinerant model relating Co doping to changes in the hot spots of the Fermi surface. We argue that the overdamped spin fluctuations provide a pairing mechanism for superconductivity in these materials.
- Received 2 December 2013
- Revised 24 April 2014
DOI:https://doi.org/10.1103/PhysRevB.89.180503
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