In-Plane Resistivity Anisotropy in an Underdoped Iron Arsenide Superconductor

Abstract

High-temperature superconductivity often emerges in the proximity of a symmetry-breaking ground state. For superconducting iron arsenides, in addition to the antiferromagnetic ground state, a small structural distortion breaks the crystal's C(4 )rotational symmetry in the underdoped part of the phase diagram. We reveal that the representative iron arsenide Ba(Fe(1)(-x)Co(x))(2)As(2) develops a large electronic anisotropy at this transition via measurements of the in-plane resistivity of detwinned single crystals, with the resistivity along the shorter b axis rho(b) being greater than rho(a). The anisotropy reaches a maximum value of ~2 for compositions in the neighborhood of the beginning of the superconducting dome. For temperatures well above the structural transition, uniaxial stress induces a resistivity anisotropy, indicating a substantial nematic susceptibility.

Filamentary superconductivity across the phase diagram of Ba(Fe,Co)2As2

“…2(b) shows that, in fact, T f l displays a non-monotonic dependence on Co doping, with a minimum for x ≈ 0.02 to 0.03. Interestingly, Jiun-Haw Chu et al 9 have recently reported a maximum electronic nematic order over the same range of Co concentrations, around the onset of bulk superconductivity (x = 0.03). This suggests a maximum orbital order around the onset of bulk SC.…”

“…2,8 However, the large electronic anisotropy revealed in Ba(Fe 1−x Co x ) 2 As 2 precisely where the crystal's C 4 rotational symmetry is broken can not be explained based on the 1% lattice distortion at T s . 9 In fact, it has been shown the presence of a C 4 structural to C 2 electronic symmetry transition in the quasi-particle interference maps of Ca(Fe 1−x Co x ) 2 As 2 . 10 This electronic symmetry transition could be a result of orbital ordering due to the above mentioned inequivalent occupation of the d xz and d yz orbitals.…”

“…10 This electronic symmetry transition could be a result of orbital ordering due to the above mentioned inequivalent occupation of the d xz and d yz orbitals. [9][10][11][12] Based on these results, we found that it is imperative to perform measurements that could simultaneously reveal the effect of spin and orbital fluctuations on the emergence of SC in iron-based superconductors. In this paper, we reveal through magnetoresistivity studies the presence of filamentary superconductivity (FLSC) over a wide range of the phase diagram of Ba(Fe 1−x Co x ) 2 As 2 (0 ≤ x ≤ 0.13), from the parent AFM compound to the optimally-doped region, and its disappearance in the over-doped region where the AFM order is suppressed.…”

Competition between superconductivity and nematic order: Anisotropy of superconducting coherence length

“…[2][3][4][5][6][7][8] In the cuprates, nematic order is signaled by the anisotropy of resistivity and bond ordered density [2][3][4][5][6] . In the pnictides, orthorhombic structure distortion is ubiquitous, and is confirmed by various tools such as neutron scattering 9 , STM 10 , transport [11][12][13] , and ARPES 14 . A natural question associated with nematic ordering is its interaction with other order parameters.…”

Anisotropy of the optical conductivity of a pnictide superconductor from the undoped three-orbital Hubbard model

“…[2][3][4][5] Studies of the in-plane resistivity 6 showed that the effect is the largest at low doping x∼2-4% in Ba(Fe 1−x Co x ) 2 As 2 , but it is present even in the undoped limit x=0 at low temperatures, i.e. in the magnetically ordered state with wavevector (π,0).…”