Anisotropy of the In-Plane Resistivity of UnderdopedBa(Fe1−xCox)2As2Superconductors

Abstract

We investigated the in-plane resistivity anisotropy for underdoped Ba(Fe(1-x)Co(x))(2)As(2) single crystals with improved quality. We demonstrate that the anisotropy in resistivity in the magnetostructural ordered phase arises from the anisotropy in the residual component which increases in proportion to the Co concentration x. This gives evidence that the anisotropy originates from the impurity scattering by Co atoms substituted for the Fe sites, rather than the so far proposed mechanisms such as the anisotropy of Fermi velocities of reconstructed Fermi surface pockets. As doping proceeds to the paramagnetic-tetragonal phase, a Co impurity transforms to a weak and isotropic scattering center.

Effects of isovalent substitution and pressure on the interplane resistivity of single-crystalBa(Fe1−xRux)2Tanatar1, Torikachvili2, Thaler3 et al. 2014Phys. Rev. B

“…The increase of the mean-free path is limited at low temperatures by elastic scattering on residual impurities. In the parent compound the loss of the spin-disorder scattering dominates and the resistivity decreases gradually below T m , particularly strongly in the cleanest annealed samples 57 . The partial gapping is responsible for an increase of the resistivity below T m in Ru-and Cosubstituted materials, see Fig.…”

Antiferromagnetic order and spin dynamics in iron-based superconductors

“…NMR experiments on 1111 family of materials also indicate the presence of a nematic phase below T s (Fu et al, 2012). However, recent scanning tunneling microscopy (Allan et al, 2013) and transport measurements (Ishida et al, 2013) suggest that the resistivity anisotropy in Co-doped BaFe 2 As 2 arises from Co-impurity scattering and is not an intrinsic property of these materials. On the other hand, ARPES measurements on Co-doped BaFe 2 As 2 (Yi et al, 2011) and NaFeAs reveal a splitting in energy between two orthogonal bands with dominant d xz and d yz character at the temperature of resistivity anisotropy in uniaxial strain detwinned samples, thereby suggesting that orbital ordering is also important for the electronic properties of iron pnictides (Krüger et al, 2009;Lee et al, 2009;Lv et al, 2009).…”

Magnetic interactions in iron superconductors: A review

“…Upon annealing, Ishida et al [76] find that the resistivity anisotropy of BaFe 2 As 2 nearly vanishes while significant anisotropy remains in Co-doped compounds. Similar results are obtained in Ba(Fe 1−x Ru x ) 2 As 2 [226].…”