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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

ρab(T) vs. T for BaFe1.9M0.1As2 (M = Co, Cu, Ni, and Mn) single crystals for P = 5–25 kbar.The insets show the evolution of Tc with pressure.
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f2: ρab(T) vs. T for BaFe1.9M0.1As2 (M = Co, Cu, Ni, and Mn) single crystals for P = 5–25 kbar.The insets show the evolution of Tc with pressure.

Mentions: Figs. 2a–b show ρab (T) as a function of pressure for Co and Ni-substituted compounds. A small increase of Tc is observed, as expected for nearly OPD samples3. For instance, Tc reaches 28.6 K at 18 kbar for M = Co, whereas the self-flux OPD compound reaches a maximum Tc of ~23 K in the same pressure range, suggesting that the In-flux samples are of high quality. On the other hand, for M = Ni, Tc only reaches 24.7 K. One can speculate that the reason the Ni-OPD sample does not achieve Tc ~ 29 K is that it introduces more disorder than cobalt9108. Indeed, the residual resistivity is higher for M = Ni. Furthermore, the highest Tc found in FeAs-based SC is obtained through out-of-plane substitution4241.


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)

ρab(T) vs. T for BaFe1.9M0.1As2 (M = Co, Cu, Ni, and Mn) single crystals for P = 5–25 kbar.The insets show the evolution of Tc with pressure.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f2: ρab(T) vs. T for BaFe1.9M0.1As2 (M = Co, Cu, Ni, and Mn) single crystals for P = 5–25 kbar.The insets show the evolution of Tc with pressure.
Mentions: Figs. 2a–b show ρab (T) as a function of pressure for Co and Ni-substituted compounds. A small increase of Tc is observed, as expected for nearly OPD samples3. For instance, Tc reaches 28.6 K at 18 kbar for M = Co, whereas the self-flux OPD compound reaches a maximum Tc of ~23 K in the same pressure range, suggesting that the In-flux samples are of high quality. On the other hand, for M = Ni, Tc only reaches 24.7 K. One can speculate that the reason the Ni-OPD sample does not achieve Tc ~ 29 K is that it introduces more disorder than cobalt9108. Indeed, the residual resistivity is higher for M = Ni. Furthermore, the highest Tc found in FeAs-based SC is obtained through out-of-plane substitution4241.

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