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Magnetic field-induced antiferromagnetism in the heavy fermion superconductor CeRhIn 5

Magnetic field-induced antiferromagnetism in the heavy fermion superconductor CeRhIn 5. Kitaoka Lab M1 Katsuyoshi Uematsu. M1 colloquium. T. Park et al ., Nature 440 , 65 (2006). G. Knebel et al ., PRB 74 , 020501 (2006). Contents. Introduction History of Superconductivity

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Magnetic field-induced antiferromagnetism in the heavy fermion superconductor CeRhIn 5

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  1. Magnetic field-induced antiferromagnetism in the heavy fermion superconductor CeRhIn5 Kitaoka LabM1 Katsuyoshi Uematsu M1 colloquium T. Park et al., Nature 440, 65 (2006) G. Knebel et al., PRB74, 020501 (2006)

  2. Contents • Introduction • History of Superconductivity • Heavy Fermion (HF) system • Experiment • Motivation • Experimental method • Results of specific heat in CeRhIn5 • Summary • Future work

  3. Introduction 1900 1920 1940 1960 1980 2000 2020 Year History of Superconductivity 200 metal Discovery of superconducting phenomenon 1911 heavy fermion system high-Tc cuprate 163 Hg-Ba-Ca-Cu-O iron-based system under high pressure （ ） 150 Hg-Ba-Ca-Cu-O Tl-Ba-Ca-Cu-O 1979 1986 Heavy fermion superconductor Bi-Sr-Ca-Cu-O 100 Transition temperature (K) Y-Ba-Cu-O 77 High-Tc cuprate superconductor SmO F FeAs 50 0.9 0.11 MgB2 La-Ba-Cu-O LaO F FeAs PuCoGa5 Nb Ge 0.11 0.89 Nb 2006 Pb CeCu2Si2 NbN LaOFeP Hg NbC 0 Iron-based high-Tc superconductor

  4. Introduction Similarity between High-Tc & HF : antiferromagnetism (反強磁性) : superconductivity (超伝導) AFM SC high-Tc cuprate heavy fermion (HF) In both superconductors, SC is related to AFM.

  5. Introduction : Heavy Fermion system 4f 5p closed shell n(r) 5d 6s r Example of Heavy Fermion system Heavy Fermion system : 重い電子系 Example of heavy fermion superconductor compounds CeCu2Si2 CePd2Si2 CeRh2Si2CeIn3CeRhIn5 UPt3UPd2Al3 PrOs4Sb12 PuCoGa5 etc Ce3+:･･･5s25p64f 1 All of HF system compounds have some f-electrons.

  6. Introduction : Heavy Fermion system D(εF) is the electronic density of states at the Fermi energy εF . m*kF e = ∝m* (effective mass) D ( ) F p 2 2 2 h What does “Heavy” mean? “Heavy” ⇒ The effective mass is large. Specific heat : C =gT [g = (2/3)p2kB2D(eF)] Susceptibility: c = c0 [c0=2mB 2D(eF)] Resistivity : r = r0 + AT n [A ∝ ∝g2] γheavy /γnormal＝ 100~ 1000

  7. Introduction : Heavy Fermion system Two main interactions of HF system RKKY interaction Kondo effect (RKKY:Rudermann-Kittel-Kasuya-Yoshida) Conductionelectron Conduction electron Jcf Polarization Jcf Jcf 4f electron (Ce) 4felectron (Ce) The interplay between two 4f electrons mediated by conduction electrons 4f and conduction electrons form a spin-singlet state. Magnetic Order Fermi Liquid

  8. Introduction : Heavy Fermion system Phase Diagram of HF system TK TRKKY ∝ W exp(-1/Jcf D(εF)) ∝ D(εF) Jcf2 As Jcf increases, ⇒AFMdisappears and SC appears (near QCP) SC Quantum instability of AFM ⇒ SC appears : antiferromagnetism (反強磁性) : superconductivity (超伝導) : heavy fermion (重い電子状態) : quantum critical point (量子臨界点) AFM SC HF QCP

  9. Introduction : Heavy Fermion system Coexistence AFM and SC (b) Wide superconducting phase CeRhIn5 (CeCu2Ge2 , CeCu2Si2) • Narrow superconducting phase • CeRh2Si2 , CePd2Si2 , CeIn3etc The coexistingAFM and SC are confirmed in HF SCs.

  10. Experiment : Motivation Phase Diagram of CeRhIn5 c a AFM +SC b H AFMdisappears like a first-order boundary. Applying magnetic field (H), SC is suppressed and AFM appears? Crystal structure of CeRhIn5 (M=Rh)

  11. Experiment : Measurement method Specific heat measurement Tc TN Specific heat : C =gT+AT3 ~ gT [g = (2/3)p2kB2D(eF)] gT AT3 : electronic specific heat : specific heat of phonon Tc At phase transition ex.) , specific heat jump is observed. Specific heat of Ce115 (P=0,H=0) ex.) paramagnetism ⇒ antiferromagnetism nomal conductivity ⇒ superconductivity Y.Onuki et al., J.Phys.Soc.Jpn. 71 162 (2002)

  12. Experiment :Specific heat of CeRhIn5 Specific heat of CeRhIn5 at H=0 H = 0(T) TN Tc At H=0, pressure is applied. Specific heat of CeRhIn5 (H=0) TN suddenly disappears. near P = 1.95GPa

  13. Experiment : Specific heat of CeRhIn5 Specific heat of CeRhIn5 at H≠0 2.73GPa 2.2 2.41 H is applied :TN :Tc H = 0(T) Atpressure is constant, H is applied. (P : 2.2 , 2.41GPa) Tcis down, and AFMappears. Specific heat of CeRhIn5 (H⊥c)

  14. Experiment : Phase diagram T-H Phase Diagram of CeRhIn5 P = 2.41 (GPa) H = 0(T) 2.41 2.73GPa P = 2.73(GPa)

  15. Experiment : Phase diagram P-TPhase Diagram of CeRhIn5 Magnetic field isapplied H = 0(T) H = 6(T) AFM is induced by the magnetic field above 2GPa.

  16. Summary H = 6(T) Applying a magnetic field suppresses SC, and AFM appears. AFM is suppressed by SC. P = 2.41 (GPa) AFMand SC are competing together.

  17. Future work H = 6(T) : 0.5 ~ 1 (K) : 2.1 ~ 2.4 (GPa) : 5 ~ 7 (T) T P H In this condition, I’ll examine the magnetic structure of CeRhIn5by NMR. NMR measurement !!

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