FisMat2017 - Submission - View

Abstract's title: Impurity effects in optimally doped oxypnictide superconductors
Submitting author: Samuele Sanna
Affiliation: University of Bologna and SPIN-CNR
Affiliation Address: Department of Physics and Astronomy
Country: Italy
Oral presentation/Poster (Author's request): Oral presentation
Other authors and affiliations: M. Moroni (Department of Physics, University of Pavia-CNISM, I-27100 Pavia, Italy), P. Carretta (Department of Physics, University of Pavia-CNISM, I-27100 Pavia, Italy), G. Allodi (Dipartimento di Fisica e Scienze della Terra, Università di Parma, I-43124 Parma, Italy), R. De Renzi (Dipartimento di Fisica e Scienze della Terra, Università di Parma, I-43124 Parma, Italy), T. Shiroka (Laboratorium fur Festkorperphysik, ETH-Honggerberg, CH-8093 Zurich, Switzerland), G. Lamura (CNR-SPIN, Corso Perrone 24, I-161526 Genova, Italy), M. Putti (Dipartimento di Fisica, Universit`a di Genova, via Dodecaneso 33, I-16146 Genova, Italy)
Abstract

Fast suppression of superconductivity occurs in optimally electron doped LaFeAsO0.89F0.11 by substituting Fe by Mn at a remarkablylow critical content xc=0.2% [1,2].

Here we show that as soon as superconductivity is destroyed the parent undoped LaFeAsO ground state is recovered: both the same stripe ordered magnetic structure and tetragonal to orthorhombic transition are detected in optimally electron doped LaFeAsO0.89F0.11 with 0.5% of Mn [3].

Recent theoretical calculations [4] display that enhanced spin correlations developing around Mn severely speed up the reduction of Tc driven by the magnetic disorder, and may quench the entire superconducting phase already at Mn concentrations below 1%. The magnetic order generated by Mn doping is efficiently stabilized due to correlation-enhanced RKKY exchange couplings between neighbouring Mn ions [3,4].

Interestingly we show that the Mn critical threshold xc for the suppression of superconductivity is rapidly increased to few percent of Mn by squeezing the volume cell by substituting La by Y or Sm (xc = 8%) [5,6]. This behavior can be explained by considering the role of the electronic correlations, which are increased in isostructural compounds with bigger unit cell volume. Correlations enhance the RKKY exchange interactions between Mn ions driving the compound with La at the verge of an electronic instability, i.e. xc tends to 0.

The LnFeAsO (Ln=lanthanide) can be considered as a formidable example of how the electronic properties of strongly correlated systems can be significantly affected by fine-tuning the correlation strength with impurities and chemical pressure.

References

[1] F. Hammerath, P. Bonfà, S. Sanna, G. Prando, R. De Renzi, Y. Kobayashi, M. Sato, and P. Carretta, Phys. Rev. B 89, 134503 (2014).

[2] F. Hammerath, M. Moroni, L. Bossoni, S. Sanna, R. Kappenberger, S. Wurmehl, A. U. B. Wolter, M. A. Afrassa, Y. Kobayashi, M. Sato, B. Buchner, and P. Carretta, Phys. Rev. B 92, 020505(R) (2015).

[3] M. Moroni, P. Carretta, G. Allodi, R. De Renzi, M. N. Gastiasoro, B. M. Andersen, P. Materne, H.-H. Klauss, Y. Kobayashi, M. Sato, and S. Sanna, Phys. Rev. B 95, 180501(R) (2017).

[4] M. N. Gastiasoro, F. Bernardini and B. M. Andersen, Phys. Rev. Lett. 117, 257002 (2016).

[5] M. Moroni, S. Sanna, et al. Phys. Rev.B 94, 054508 (2016).

[6] G. Lamura, T. Shiroka, S. Bordignon, S. Sanna et al., Phys Rev. B 94, 214517 (2016).