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Possible unconventional superconductivity in substituted BaFe2As2 revealed by magnetic pair-breaking studies.

Rosa PF, Adriano C, Garitezi TM, Piva MM, Mydeen K, Grant T, Fisk Z, Nicklas M, Urbano RR, Fernandes RM, Pagliuso PG - Sci Rep (2014)

Bottom Line: An ESR signal, indicative of the presence of localized magnetic moments, is observed only for M = Cu and Mn compounds, which display very low SC transition temperature (Tc) and no SC, respectively.From the ESR analysis assuming the absence of bottleneck effects, the microscopic parameters are extracted to show that this reduction of Tc cannot be accounted by the Abrikosov-Gorkov pair-breaking expression for a sign-preserving gap function.Our results reveal an unconventional spin- and pressure-dependent pair-breaking effect and impose strong constraints on the pairing symmetry of these materials.

View Article: PubMed Central - PubMed

Affiliation: 1] Instituto de Física "Gleb Wataghin", UNICAMP, Campinas-SP, 13083-859, Brazil [2] University of California, Irvine, California 92697-4574, USA.

ABSTRACT
The possible existence of a sign-changing gap symmetry in BaFe2As2-derived superconductors (SC) has been an exciting topic of research in the last few years. To further investigate this subject we combine Electron Spin Resonance (ESR) and pressure-dependent transport measurements to investigate magnetic pair-breaking effects on BaFe1.9M0.1As2 (M = Mn, Co, Cu, and Ni) single crystals. An ESR signal, indicative of the presence of localized magnetic moments, is observed only for M = Cu and Mn compounds, which display very low SC transition temperature (Tc) and no SC, respectively. From the ESR analysis assuming the absence of bottleneck effects, the microscopic parameters are extracted to show that this reduction of Tc cannot be accounted by the Abrikosov-Gorkov pair-breaking expression for a sign-preserving gap function. Our results reveal an unconventional spin- and pressure-dependent pair-breaking effect and impose strong constraints on the pairing symmetry of these materials.

No MeSH data available.


Related in: MedlinePlus

In-plane electrical resistivity, ρab (T), for BaFe1.9M0.1As2 (M = Mn, Cu, Ni, Co) single crystals.The arrows show the minima of the first derivative in the vicinity of the SDW transition.
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f1: In-plane electrical resistivity, ρab (T), for BaFe1.9M0.1As2 (M = Mn, Cu, Ni, Co) single crystals.The arrows show the minima of the first derivative in the vicinity of the SDW transition.

Mentions: Fig. 1 displays the in-plane electrical resistivity, ρab (T), at ambient pressure for the selected single crystals. A linear metallic behavior is observed at high-T and the SDW phase transition of the parent compound is suppressed for all substitutions. A slight upturn is still present (arrows in Fig. 1), as typically found for substituted samples of Ba122 slightly below the OPD concentration3. As T is further decreased, SC emerges with the onset of Tc, defined as the temperature at which dρab/dT = 0, at 26.1 K, 22.2 K, and 3.8 K for Co, Ni, and Cu substitutions, respectively. On the other hand, no Tc is observed for M = Mn.


Possible unconventional superconductivity in substituted BaFe2As2 revealed by magnetic pair-breaking studies.

Rosa PF, Adriano C, Garitezi TM, Piva MM, Mydeen K, Grant T, Fisk Z, Nicklas M, Urbano RR, Fernandes RM, Pagliuso PG - Sci Rep (2014)

In-plane electrical resistivity, ρab (T), for BaFe1.9M0.1As2 (M = Mn, Cu, Ni, Co) single crystals.The arrows show the minima of the first derivative in the vicinity of the SDW transition.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4150111&req=5

f1: In-plane electrical resistivity, ρab (T), for BaFe1.9M0.1As2 (M = Mn, Cu, Ni, Co) single crystals.The arrows show the minima of the first derivative in the vicinity of the SDW transition.
Mentions: Fig. 1 displays the in-plane electrical resistivity, ρab (T), at ambient pressure for the selected single crystals. A linear metallic behavior is observed at high-T and the SDW phase transition of the parent compound is suppressed for all substitutions. A slight upturn is still present (arrows in Fig. 1), as typically found for substituted samples of Ba122 slightly below the OPD concentration3. As T is further decreased, SC emerges with the onset of Tc, defined as the temperature at which dρab/dT = 0, at 26.1 K, 22.2 K, and 3.8 K for Co, Ni, and Cu substitutions, respectively. On the other hand, no Tc is observed for M = Mn.

Bottom Line: An ESR signal, indicative of the presence of localized magnetic moments, is observed only for M = Cu and Mn compounds, which display very low SC transition temperature (Tc) and no SC, respectively.From the ESR analysis assuming the absence of bottleneck effects, the microscopic parameters are extracted to show that this reduction of Tc cannot be accounted by the Abrikosov-Gorkov pair-breaking expression for a sign-preserving gap function.Our results reveal an unconventional spin- and pressure-dependent pair-breaking effect and impose strong constraints on the pairing symmetry of these materials.

View Article: PubMed Central - PubMed

Affiliation: 1] Instituto de Física "Gleb Wataghin", UNICAMP, Campinas-SP, 13083-859, Brazil [2] University of California, Irvine, California 92697-4574, USA.

ABSTRACT
The possible existence of a sign-changing gap symmetry in BaFe2As2-derived superconductors (SC) has been an exciting topic of research in the last few years. To further investigate this subject we combine Electron Spin Resonance (ESR) and pressure-dependent transport measurements to investigate magnetic pair-breaking effects on BaFe1.9M0.1As2 (M = Mn, Co, Cu, and Ni) single crystals. An ESR signal, indicative of the presence of localized magnetic moments, is observed only for M = Cu and Mn compounds, which display very low SC transition temperature (Tc) and no SC, respectively. From the ESR analysis assuming the absence of bottleneck effects, the microscopic parameters are extracted to show that this reduction of Tc cannot be accounted by the Abrikosov-Gorkov pair-breaking expression for a sign-preserving gap function. Our results reveal an unconventional spin- and pressure-dependent pair-breaking effect and impose strong constraints on the pairing symmetry of these materials.

No MeSH data available.


Related in: MedlinePlus