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Superconducting properties in filled-skutterudite PrOs 4 Sb 12

Superconducting properties in filled-skutterudite PrOs 4 Sb 12. Kitaoka Lab. M1 Takayuki Nagai. references. ・ H.Kotegawa et al ,Phys.Rev.Lett. 90 ,027001 (2003) ・ M.Yogi et al ,Phys.Rev. B 67 ,180501(R) (2003). Filled-skutterudite : 充填スクッテルダイト. Abstract. abstract.

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Superconducting properties in filled-skutterudite PrOs 4 Sb 12

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  1. Superconducting properties infilled-skutterudite PrOs4Sb12 Kitaoka Lab. M1Takayuki Nagai references ・H.Kotegawa et al,Phys.Rev.Lett. 90,027001 (2003) ・M.Yogi et al,Phys.Rev. B 67,180501(R) (2003) Filled-skutterudite : 充填スクッテルダイト

  2. Abstract abstract ・Filled-skutterudite compounds show rich properties metal-insulator transition, heavy fermion behavior,and superconductivity etc. (LaOs4Sb12,PrOs4Sb12, PrRu4Sb12etc.) ・PrOs4Sb12shows heavy-fermion-like behavior and anomalous superconductivity in many experiments. ・The related compounds, LaOs4Sb12,LaRu4Sb12and PrRu4Sb12 have been reported as conventional BCS superconductors. Metal-insulator transition : 金属-絶縁体転移 Heavy-fermion (HF) compound : 重い電子系化合物

  3. Outline Outline • Introduction - Filled-skutterudite structure - Crystal electric field - Nuclear Quadrupole Resonance technique • Experiments • Summary

  4. Introduction : Filled-skutterudite / Crystal structure Highertemperature Lower temperature rare earth transition metal pnictogen The cage made by a rare earth atom and 12 pnictogen atoms forms bcc-type crystal lattice Thermoelectric effect Crystal structure Application ・refrigerator ・waste heat recovery etc. Filled-skutterudite compounds show rich properties. ・metal-insulator transition ・heavy-fermion (HF) behavior ・superconducting (SC) transition Thermoelectric effect : 熱電効果

  5. Introduction : Crystal electric field Introduction : Crystal electric field L-S coupling : スピン-軌道相互作用 : orbital angular momentum : spin angular momentum Crystal electric field : 結晶場 Interaction between electrons and ions. PrOs4Sb12 Crystal electric field effect L-S coupling J=6 (13) (111K , doublet) Pr3+-4f2 J=5 (11) (65K , triplet) J=4 (9) (6K , triplet) magnetic (0K , singlet) non-magnetic Very small split → Magnetic fluctuations Magnetic fluctuation : 磁気揺らぎ T.Hotta et al,Phys. Rev.Letter. 94 (2005) 067003

  6. Introduction : Filled-skutterudite compounds Introduction : Filled-skutterudite compounds / PrOs4Sb12 PrOs4Sb12 PrRu4Sb12 ？ BCS TC=1.3K TC=1.85K LaOs4Sb12 LaRu4Sb12 BCS BCS TC=0.74K TC=3.58K PrOs4Sb12 ・zero resistivity ・Meissner effect ・Jump of specific heat ・ First Pr-based heavy-fermion superconductor E.D.Bauer et al,Phys. Rev. B 65 (2002) 100506

  7. Introduction : Nuclear Quadrupole Resonance Introduction : Nuclear Quadrupole Resonance e + Sb-NQR spectrum of PrOs4Sb12 ・123Sb(I=7/2) ・121Sb(I=5/2) 3νQ 2νQ 121Sb (123Sb) has 2 (3) NQR transitions. 2νQ νQ νQ Charge distribution is not spherical symmetry. Nuclear Quadrupole Resonance : 核四重極共鳴

  8. Experiments : Nuclear spin-lattice relaxation Energy T1 Nuclear spin-lattice relaxation 核スピン－格子緩和

  9. Experiments : Nuclear spin-lattice relaxation BCS superconductor : LaOs4Sb12 Normal state La

  10. Experiments : Nuclear spin-lattice relaxation BCS superconductor : LaOs4Sb12 SC state TC Coherence peak NMR can detect low energy excitation around the Fermi surface.

  11. Experiments :Gap structure of anisotropic rsuperconductor Experiments: Gap structure of anisotropic superconductors Observed in HF superconductors. Line-node Gap equation 1/T1∝T3 TC Point-node Gap equation 1/T1∝T5 G.-q.Zheng et al,PRL 86 4664(2001) Anisotropic superconductor : 異方的超伝導体

  12. Experiments : Spin-lattice-relaxation time T1 LaOs4Sb12 vs. PrOs4Sb12 LaOs4Sb12 ・Normal State →T1T: const. ・SC State → Coherence peak at TC and Exponential T dependence of 1/T1 Conventional BCS superconductor. LaOs4Sb12 PrOs4Sb12

  13. Experiments : Spin-lattice-relaxation time T1-2 CeCu2Si2 , CeIrIn5vs.PrOs4Sb12 Y.Kawasaki et al,PRB 66 (2002) 224502 IsotropicHF superconductor? CeIrIn5 CeCu2Si2 PrOs4Sb12 G.-q.Zheng et al,PRL 86 4664(2001) CeCu2Si2 , CeIrIn5 ・SC state 1/T1 is proportional to T3 →anisotropic HF superconductor

  14. Experiments : Spin-lattice-relaxation time T1-3 PrRu4Sb12 vs. PrOs4Sb12 TC PrOs4Sb12 M.Yogi et al, PRL 90 027001 (2003) T<<70K T>>70K H. Kotegawa et al, PRL 90 027001 (2003) T<<6K T>>6K magnetic TC=1.85K 70K magnetic 6K non-magnetic TC=1.3K non-magnetic : Electrons

  15. Results TC TC Crystal electric field plays an important role. PrOs4Sb12 PrRu4Sb12 PrOs4Sb12 isn’t a conventional BCS superconductor. Isotropic-HF super conductor BCS TC=1.3K TC=1.85K LaOs4Sb12 LaRu4Sb12 BCS BCS TC=0.74K TC=3.58K

  16. Summary Summary • From temperature dependence of nuclear-spin-relaxation time T1, PrOs4Sb12 is notconventional BCS superconductor but HF-like-isotropic superconductor. • Crystal electric field plays an important role in the superconductivity of PrOs4Sb12 .

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