#### Publication Date

4-1-2018

#### Department

Physics and Astronomy; Ames Laboratory

#### Campus Units

Physics and Astronomy, Ames Laboratory

#### Report Number

IS-J 9672

#### DOI

10.1103/PhysRevB.97.140508

#### Journal Title

Physical Review B

#### Volume Number

97

#### Issue Number

14

#### First Page

140508

#### Abstract

Controlled pointlike disorder introduced by 2.5-MeV electron irradiation was used to probe the superconducting state of single crystals of CaK(Fe1-x Ni-x)(4)As-4 superconductor at x = 0 and 0.05 doping levels. Both compositions show an increase of the residual resistivity and a decrease of the superconducting transition temperature, T-c, at the rate of dT(c)/d rho(T-c)approximate to 0.19 K/(mu Omega cm) for x = 0 and 0.38 K/(mu Omega cm) for x = 0.05, respectively. In the Ni-doped compound (x = 0.05), the coexisting spin-vortex crystal (SVC) magnetic phase is suppressed at the rate of dT(N)/d rho(T-N) approximate to 0.16 K/(mu Omega cm). The low-temperature variation of London penetration depth is well approximated by the power-law function, Delta lambda(T) = AT(n), with n approximate to 2.5 for x = 0 and n approximate to 1.9 for x = 0.05 in the pristine state. Detailed analysis of lambda(T) and T-c evolution with disorder is consistent with two effective nodeless energy gaps in the density of states due to robust s(+/-) pairing. Overall the behavior of CaK(Fe1-xNix)(4)As-4 at x = 0 is similar to a slightly overdoped Ba1-y K-y Fe2As2 at y approximate to 0.5, and at x = 0.05 to an underdoped composition at y approximate to 0.2.

#### Language

en

#### Department of Energy Subject Categories

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY

#### Publisher

Iowa State University Digital Repository, Ames IA (United States)