1 / 21

Mössbauer Spectroscopy of Iron-Based Superconductors

This research article explores the use of Mössbauer spectroscopy to study iron-based superconductors, including their phase diagram, charge density wave (CDW) and electric field gradient wave (EFGW) properties. The study focuses on specific compounds such as FeSe, BaFe2As2, and SmFeAsO1-xFx.

terrygary
Download Presentation

Mössbauer Spectroscopy of Iron-Based Superconductors

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Nadprzewodniki na bazie żelaza w świetle badań metodą spektroskopii mössbauerowskiej Artur Błachowski1, Kamila Komędera1, Krzysztof Ruebenbauer1, Jan Żukrowski2 1Laboratorium Spektroskopii Mössbauerowskiej, Instytut Fizyki, Uniwersytet Pedagogiczny, ul. Podchorążych 2, 30-084 Kraków 2Akademickie Centrum Materiałów i Nanotechnologii, Akademia Górniczo-Hutnicza, al. Mickiewicza 30, 30-059 Kraków ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

  2. •H2S 155 GPa 30 GPa) •FeSe s-l Up to now the maximum Tsc is 56 K Published on Web 02/23/2008

  3. Fe-based Superconducting Families pnictogens:P, As chalcogens:S, Se, Te 111112211111 LnO(F)FeAsAFe2As2AFeAs FeTe(Se,S) Ln = La, Ce, Pr, Nd, Sm, Gd … A = Ca, Sr, Ba, Eu, K A = Li , Na Tscmax = 56 K 47 K 18 K 15 K

  4. Layered Structure of Fe-based Superconductors Spin density wave (SDW) magnetic order --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Phase Diagram Holes, electrons or isovalent doping BaFe2As2 Ba1-xKxFe2As2 BaFe2-xCoxAs2 BaFe2As2-xPx Parent Compounds SDW Doped Compounds  Superconductors

  5. Mössbauer Spectroscopy -ray energy is modulated by the Doppler effect due to the source motion vs. absorber Source (e.g. 57Co/Rh) Absorber (57Fe) Detector – v +v 1 mm/s 48neV

  6. Hyperfine Interactions between Nuclei and Electrons  Mössbauer Parameters Electric Monopole InteractionIsomer Shift Electric Quadrupole InteractionQuadrupole Splitting Magnetic Dipole InteractionMagnetic Splitting

  7. Charge density wave (CDW) - spatial modulation of the electron charge density Electric field gradient wave (EFGW) - spatial modulation of the electric field gradient The Mössbauer spectroscopy is sensitive to the charge (electron) distribution around the resonant nucleus via the isomer shift and the electric quadrupole interaction.

  8. Charge density wave (CDW) as seen by Mössbauer Spectroscopy Construction of Mӧssbauer spectrum forsinusoidal CDW (a) one period of CDW (b) partial sub-spectra having the isomer shift proportional to amplitude of CDW (c) the overall spectrum (d) histogram of the isomer shift (charge-density) distribution. J.Cieślak, S.M.Dubiel, Nuclear Instr. Methods B 101, 295 (1995) In our case-A signature of CDW is seen as the excess of the absorber line width. One can estimate variation (dispersion) of the electron densityon the resonant nuclei (around average value) caused by existing CDW. Γ– absorber line width –unbroadened line width –calibration constant

  9. Electric field gradient wave (EFGW) as seen by Mössbauer Spectroscopy  - quadrupole coupling constant with 57Fe Mössbauer spectraDistributions of quadrupole shiftShape of EFGW

  10. Mössbauer Spectroscopy Laboratory, Pedagogical University, Kraków, Poland dr Aleksandra Jasek mgr Kamila Komędera doktorantka, IV rok

  11. Ba1-xKxFe2As2 parent compound BaFe2As2 superconductorTsc = 38K dopingK Tetragonal unit cell and phase diagram of Ba1-xKxFe2As2

  12. 57Fe Mössbauer spectra A.K.Jasek, K.Komędera, A.Błachowski, K.Ruebenbauer, Z.Bukowski, J.G.Storey, J.Karpinski, J. Alloys Compd.609, 150 (2014) Difference in total molar specific heat coefficients between superconductor and parent compound. Inset shows electronic specific heat coefficient of superconductor.

  13. 57Fe Mössbauer spectra of theBa0.6K0.4Fe2As2 (TSC = 38 K) acrosstransition to the superconducting state. Difference in total molar specific heat coefficients between superconductor and parent compound. Inset shows electronic specific heat coefficient of superconductor.

  14. Ba0.6K0.4Fe2As2 (TSC = 38 K) Shape of EFGW electric field gradient wave (delectrons density variation) Mössbauer spectra parameters S– total spectrum shift versus α-Fe Δ0– constant component of quadrupole splitting Γ – absorber line width tA– dimensionless absorber resonant thickness Relative recoilless fraction f/f0 (normalized to f0 at 4.2 K) Dispersion of CDW charge density wave (s electrons density variation)

  15. SmFeAsO1-xFx parentcompoundSmFeAsO dopingF superconductivityTsc= 55K Tetragonal unit cell of SmFeAsO Phase diagram of SmFeAsO1-xFx A.J. Drew et al., Nature Materials 8, 310(2009) Y. Kamiharaet al., New J. Phys. 12, 033005 (2010) our sample – SmFeAsO0.91F0.09

  16. SmFeAsO0.91F0.09 Resistivity and magnetic susceptibility Tsc 47 K 57Fe Mössbauer spectroscopy magnetic spectral broadening below 28 K A.K.Jasek, K.Komędera, A.Błachowski, K.Ruebenbauer, H.Lochmajer, N.D.Zhigadlo, and K.Rogacki, J. Alloys Compd.658, 520 (2016)

  17. 57Fe Mössbauer spectra of SmFeAsO0.91F0.09(Tsc ≈ 47 K) across transition to the superconducting state Resistivity Magnetic susceptibility

  18. SmFeAsO0.91F0.09 (Tsc ≈ 47 K) Mössbauer spectra parameters Shape of EFGW electric field gradient wave (delectrons density variation) Relative recoilless fractionf/f0 (normalized tof0at 28 K) Dispersion of CDW charge density wave (s electrons density variation)

  19. Comparison between charge density modulation changes during superconducting transition in Ba0.6K0.4Fe2As2(hole doping) SmFeAsO0.91F0.09(electron doping) EFGW EFGW CDW CDW  K

  20. Conclusions Ba1-xKxFe2As2 and SmFeAsO1-xFx The Mössbauer spectroscopy is sensitive to the superconducting transition in Fe-based superconductors via change of the electron charge density modulation, which is seen via dispersion of isomer shift (CDW caused by s electrons) and via distribution of electric field gradient (EFGW caused by d electrons). Shape and amplitude of EFGW and CDW are strongly perturbed at the superconducting transition. Namely, all modulations are strongly changed at critical temperature due to the superconducting gap opening and subsequent formation of Cooper pairs. However dispersion of the charge density and EFGW shape behave in the opposite ways for these two superconductors. References A.K.Jasek, K.Komędera, A.Błachowski, K.Ruebenbauer, Z.Bukowski, J.G.Storey, J.Karpinski, Electric field gradient wave (EFGW) in iron-based superconductor Ba0.6K0.4Fe2As2 studied by Mössbauer spectroscopy, J. Alloys Compd.609, 150 (2014) A.K.Jasek, K.Komędera, A.Błachowski, K.Ruebenbauer, H.Lochmajer, N.D.Zhigadlo, K.Rogacki, Change of the charge modulation during superconducting transition in SmFeAsO0.91F0.09 seen by 57Fe Mössbauer spectroscopy, J. Alloys Compd.658, 520 (2016)

More Related