Physics and Astronomy, Ames Laboratory
Journal or Book Title
Physical Review B
Using inelastic neutron scattering, we show that the onset of superconductivity in underdoped Ba(Fe1−xCox)2As2 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 x=0.04 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.
American Physical Society
Tucker, G. S.; Fernandes, R. M.; Pratt, D. K.; Thaler, A.; Ni, N.; Marty, K.; Christianson, A. D.; Lumsden, M. D.; Sales, B. C.; Sefat, A. S.; Bud’ko, Sergey L.; Canfield, Paul C.; Kreyssig, Andreas; Goldman, Alan I.; and McQueeney, Robert J., "Crossover from spin waves to diffusive spin excitations in underdoped Ba(Fe1-xCox)(2)As-2" (2014). Physics and Astronomy Publications. 600.