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A New High Temperature Superconductor PuCoGa5 and its Implications

A New High Temperature Superconductor PuCoGa5 and its Implications. Yunkyu Bang (Chonnam National University) Collaborators (LANL) : A.V. Balatsky, M. Graf (theory) N. Curro , J.D. Thompson, J. Sarrao, E. Bauer (experiment). Summary: PuCoGa5 is an unconventional SC (d-wave)

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A New High Temperature Superconductor PuCoGa5 and its Implications

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  1. A New High Temperature Superconductor PuCoGa5 and its Implications Yunkyu Bang (Chonnam National University) Collaborators (LANL): A.V. Balatsky, M. Graf (theory) N. Curro , J.D. Thompson,J. Sarrao, E. Bauer (experiment)

  2. Summary: PuCoGa5 is an unconventional SC (d-wave) Magnetic fluctuations (AFM) mediated pairing This material is a strongly correlated f-electron metal (HF) Tc  20 K , intermediate between HF and HTSC Pseudo gap energy  20 K , intermediate between HF and HTSC Q: Can we extend the results of PuCoGa5 to HTSC ? A: ?

  3. PuCoGa5 Superconductivity J. L. Sarrao et al., Nature 420, 297 (2002) perfect diamagnetism (small Meissner effect) and zero resistivity below Tc=18.5K  C/T  bulk superconductivity  assuming BCS weak coupling, C/Tc=1.43   =77 mJ/molK2

  4. Important questions: Pairing symmetry Conventional or Unconventioanl ? (s-wave or non s-wave ?) Pairing glue phonons or non-phonons ? If phonon mediated s-wave SC (ΘD  240 K)  not interesting If unconventional SC  very exciting material (why ?)

  5. Unconventional SC : Tc ~ 1K in Heavy FermionSC • Tc ~ 100K in cuprates HTSC • Long standing question : Why such a big difference by two orders ? • PuCoGa5 might bridge the missing gap • 1. Tc ~ 20K • 2. the highest Tc among the f-electron based compounds; • Previous record was ~2 K in CeCoIn5 • 3. γ ~70-90 mJ/mol K2 strong correlation (HF )

  6. Isostructural to CeM(Co,Rh,Ir)In5 CeCoIn5 PuCoGa5

  7. Neutron scattering data (P=0) by W. Bao(quasi 2D AFM fluctuations)

  8. Phases in CeRhIn5 under Pressure T. Mito et al.. PRB 63, 220507 (2001) Pressure up Kawasaki et al, PRL 91 (2003) Heeger et al, PRL 84 (2001)

  9. CeCoIn5 CeCoIn5 (Tc=2.3K): Cp,  and 1/T1 G.-q. Zheng et al., PRL 86, 4664 (2001) ~T3 ;lines of node •  T1.06 (to 15-20 K) • above Tc=2.3 K, C/T  –lnT (to 8K) and  Indicating near QC (2D AFM)

  10. Unconventional Superconductivity in CeCoIn5 4-fold line nodes; D-wave Movshovich et al PRL 2001

  11. CeCoIn5 and Relationship to CeRhIn5 CeIn3 NFL Sidorov et al, PRL 89 (2002) CePd2Si2 N D Mathur et al, Nature, vol393, p39,1998

  12. HF SC (AFM) NFL AF FL QCP Magnetic Origin

  13. Pairing Glue ? (1) Phonon mediated superconductivity as in A-15 compound (eg. Nb3Sn) • D240 K from fitting of C(T) for T > Tc • McMillan Tc formula : * =0.1 and  =0.5 or 1.0  Tc= 2.4-13.8K (2)Spin fluctuations mediated superconductivity • Xrystal structure isostructural to CeMIn5 • Pu 5-f-electrons  FS • (band calculations by I. Opahle et al, PRL 90, 157001 (2003) and T. Maehira et al, PRL, 90, 207007 (2003).)

  14. Strategy : fit exp(T) with candidate boson scattering for its functional form as well as the magnitude of exp(T)  best boson, ch, and Tc saturation T4/3 ~

  15. Resistivity fitting with two models: phonon and spin fluctuations Spectral density of Boson

  16. Phonon model : Einstein phonon Fitting with Experiment

  17. Shunted resister model : Phonon scattering is very unlikely to explain exp (T) .

  18. Spin fluctuations model : Fitting with Experiment Bang et al PRB 70 (2004)

  19. 1.2 CeCoIn 5 20 AMGa 1.0 5 300 (A=U, Pu; M=Co, Rh) 250 15 CeCoIn 0.8 5 cm) ) 200 PuCoGa a a /g T T 1 max mW 5 sf max (T 10 ( 0.6 /r 150 0.04 r (T) (mol-K/mJ) r 100 UCoGa 0.4 5 0.02 5 50 g -1 0.2 0 0 0.00 0 200 400 600 800 0 100 200 300 T (K) T (K) max 0.0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 T/T max Energy Scale Tuning in CeCoIn & AMGa 5 5 (J Sarrao et al, J Phys: Cond Matt 15, s 2275 (2003)) • r common “ S ” - shape of (T) curve suggests role of spin fluctuations • w Increase in bandwidth à à Tc sf • no SC in UCoGa5 is due to a large imp effect Magnetic fluc. = common scattering source for 1K to 20K of Tc

  20. Pairing Symmetry ?

  21. Symmetry Probes : C(T)/T Penetration depth ((T)) NMR 1/T1 Density of states Thermal conductance (κ(T)) Tunneling Josephson Tunneling : direct phase probe

  22. Mito et al, PRB 63 (2001) 1/T1 , the best probe to see the dos at low temp ~T3 ;lines of node ~T3 Impurity state Zheng et al, PRL 86 (2001)

  23. Fig.8. The normalized Knight shifts K(T)/Kn. Solid lines are theoretical calculations for S-wave with varying concentrations of magnetic impurities of unitary limit (c=0). The normalized experimental data are with (blue stars) and without (red circles) subtraction of a constant part. Figure 5. Normalized Knight shift K(T)/Kn. Red circles are 59Co data. Solid lines are theoretical calculations for D-wave with varying concentrations of unitary impurities (c=0).

  24. Figure 7. Normalized 1/T1. Red circles are 59Co data. Solid lines are theoretical calculations for S- wave with varying concentrations of magnetic impurities of unitary limit (c=0). Figure 4. Normalized 1/T1. Red circles are 59Co data. Solid lines are theoretical calculations for D-wave with varying concentrations of unitary impurities (c=0).

  25. Curro et al, Nature 434, 2005 Unconventional d-wave SC (b) (T1T) -1 /(T1T) -10 versus T/Tc for PuCoGa5, as well as for the unconventional superconductors YBa2Cu3O7, (Tc = 92 K)7 and CeCoIn5, (Tc=2.3 K)27 and the s-wave superconductors Al (Tc=1.178 K)8, and MgB2, (Tc=39.2 K)11. The normalization constant (T1T)-1 0 is given by the value of (T1T)-1 at 1.25Tc (see Methods).

  26. Curro et al, Nature 434, 2005

  27. Schematic Evolution of Bandwidths across the Period Table From J.D. Thompson Electrons in the unfilled shell become progressively more localized in the sequence 5d  4d  3d  5f  4f  suggests an alternative way to ‘organize’ the periodic table

  28. PuRhGa5 =8.5K 20 /Tc = 5 for PuRhGa5 20 /Tc = 8 for PuCoGa5 Onuki et al, 2005

  29. Pseudo-Gapin PuRhGa5 Very similar to underdoped HTC cuprates

  30. Sakai et al 2005

  31. PuCoGa5: PuRhGa5 2/Tc ~8, 2/Tc ~5 C/Tc ~ 90mJ/molK2 , ~ 45 mJ/molK2 1/T1T QC QD

  32. Conclusion: Unconventional SC from 1K to 20 K may have an unifying mechanism of the magnetic fluc. mediated pairing near magnetic QCP. PG behavior in HF and PuMGa5 can be understood with the mag correlation. Tc and T* are controlled by the mag. energy scales. Can we jump into the HTSC ?

  33. HTSC Cuprates HF SC (AFM) NFL NFL T PG AF FL FL AF SC QCP QCP Magnetic Origin QCP Origin ? Some difference in phase diagrams for HF and HTSC.

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