Universality and unconventional enhancement of flux-flow resistivity in Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2

• Main Authors: Huang, Xinyi, Haney, D. J, Singh, Y. P, Hu, T, Xiao, H, Wen, Hai-Hu, Dzero, M, Almasan, Carmen. C
• Format: Journal Article
• Language: English
• Published: 06-12-2016
• Subjects: Physics - Strongly Correlated Electrons; Physics - Superconductivity
• DOI: 10.48550/arxiv.1612.01961

Phys. Rev. B 95, 184513 (2017) Measurements of the current-voltage characteristics were performed on
Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ single crystals with doping level $0.044 \leq x
\leq 0.1$. An unconventional increase in the flux-flow resistivity $\rho_{\rm
ff}$ with decreasing magnetic field was observed across this doping range. Such
an abnormal field dependence of flux-flow resistivity is in contrast with the
linear field dependence of $\rho_{\rm ff}$ in conventional type-II
superconductors, but is similar to the behavior recently observed in the
heavy-fermion superconductor CeCoIn$_5$. A significantly enhanced $\rho_{\rm
ff}$ was found for the x=0.06 single crystals, implying a strong
single-particle energy dissipation around the vortex cores. At different
temperatures and fields and for a given doping concentration, the normalized
$\rho_{\rm ff}$ scales with normalized field and temperature. The doping level
dependence of these parameters strongly suggests that the abnormal upturn
flux-flow resisitivity is likely related to the enhancement of spin
fluctuations around the vortex cores of the optimally doped samples.