FisMat2017 - Submission - View

Abstract's title: Effect of proton irradiation on the normal state low-energy excitations of Ba(Fe1−xRhx)2As2 superconductors
Submitting author: Matteo Moroni
Affiliation: Department of Physics, University of Pavia-CNISM
Affiliation Address: Via Bassi, 6, I-27100 Pavia, Italy, Pavia,
Country: Italy
Oral presentation/Poster (Author's request): Oral presentation
Other authors and affiliations: L. Gozzelino, G. Ghigo: Istituto Nazionale di Fisica Nucleare, Sez. Torino, Torino 10125, Italy ; Politecnico di Torino, Dept. of Applied Science and Technology, 10129 Torino, Italy. M. A. Tanatar, R. Prozorov, P. C. Canfield: Ames Laboratory, Department of Physics and Astronomy, Ames, Iowa 50011, USA. P. Carretta: Department of Physics, University of Pavia-CNISM, I-27100 Pavia, Italy.

We present a 75As Nuclear Magnetic Resonance (NMR) and resistivity study [1] of the effect of 5.5 MeV proton irradiation on the optimal electron doped (x = 0.068) and overdoped (x = 0.107) Ba(Fe1−xRhx)2As2 iron based superconductors. While the proton induced defects only mildly suppress the critical temperature and increase residual resistivity [1,2]  in both compositions, sizable broadening of the NMR spectra was observed in the optimally doped samples (x=0.068) at low temperature. The Curie Weiss temperature dependence of the line width suggests the onset of ferromagnetic correlations coexisting with superconductivity at the nanoscale. The effect is absent in the overdoped sample owing to the absence of significant spin correlations. Futhermore spin-spin relaxation rate (1/T2) measurements revealed that the low-frequency fluctuations observed in several families of iron-based superconductors [3,4], and whose nature is presently subject of debate, are damped by the irradiation induced impurities, consistently with the hypothesis that they could be associated with the presence of nematic fluctuations between (0, π) and (π,0) nematic phases. 


[1] M. Moroni et al, arXiv:1705.06905
[2] Y. Nakajima et al, Phys. Rev. B 82, 220504(R).
[3] L. Bossoni et al, Phys. Rev. B 93, 224517 (2016).
[4] L. Bossoni et al, Phys. Rev. B 88, 100503(R) (2013).