Electronic nematic correlations in the stress-free tetragonal state ofBaFe2−xNixAs2

Abstract

We use transport and neutron scattering to study electronic, structural, and magnetic properties of the electron-doped BaFe2−xNixAs2 iron pnictides in uniaxial strained and external stress free detwinned state. Using a specially designed in-situ mechanical detwinning device, we demonstrate that the in-plane resistivity anisotropy observed in the uniaxial strained tetragonal state of BaFe2−xNixAs2 below a temperature T * , previously identified as a signature of the electronic nematic phase, is also present in the stress free tetragonal phase below T * * (< T * ). By carrying out neutron scattering measurements on BaFe2As2 and BaFe1.97Ni0.03As2, we argue that the resistivity anisotropy in the stress free tetragonal state of iron pnictides arises from the magnetoelastic coupling associated with antiferromagnetic order. These results thus indicate that the local lattice distortion and nematic spin correlations are responsible for the resistivity anisotropy in the tetragonal state of stress free iron pnictides, and suggest that resistivity anisotropy, spin excitation anisotropy, and orbital ordering found in the paramagnetic state of uniaxial strained iron pnictides are due to the externally applied uniaxial strain and its coupling to nematic susceptibility.

Spin anisotropy due to spin-orbit coupling in optimally hole-dopedBa0.67K0.33Fe2As2

“…56 and 4 . (c) Resistivity anisotropy (ρa − ρ b )/(ρa + ρ b ) of BaFe1.904Ni0.096As2 and Ba0.67K0.33Fe2As2 under uniaxial pressure of P = 15 MPa measured using a mechanical clamp that can vary applied pressure in-situ 47,57 . (d) Elastoresistance |2m66| for optimally-doped BaFe1.91Ni0.09As2, Ba0.6K0.4Fe2As2, and BaFe2As1.4P0.6, adapted from Ref.…”

Uniaxial pressure effect on the magnetic ordered moment and transition temperatures in BaFe2−xTxAs2 ( T=Tam1, Song2, Man3 et al. 2017Phys. Rev. BSelf Cite292240View full textAdd to dashboardCite

“…Uniaxial pressure has been used to mechanically detwin single crystals by compressing along one axis of the orthorhombic lattice, creating a preferred orientation for microscopic domains [27][28][29]. However, even the modest amount of pressure necessary for detwinning (∼10 MPa) also induces a significant (∼1-2 K) upward shift of T N in electron-doped BaFe 2 As 2 [30][31][32][33][34], and changes T s into a crossover with orthorhombic lattice distortion at all temperatures [35]. One study combining a phenomenological Ginsburg-Landau model with density functional theory (DFT) calculations under uniaxial strain suggest that the magnetic ordered moment of BaFe 2 As 2 decreases under pressure [36], in agreement with the experimentally observed decrease in the combined magnetic scattering at (±1, 0, L) and (0, ±1, L) [30,31].…”

Orbital selective neutron spin resonance in underdoped superconducting NaFe0.985Co0.015As

“…The clear spin excitation anisotropy above T s is likely due to the applied uniaxial pressure as discussed in Refs. 47,48 . As a function of decreasing temperature, the magnetic scattering anisotropy starts to build up below T * , saturates at temperatures slightly below T N , and shows no anomaly across T c .…”