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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 CeRhIn5 Kitaoka LabM1 Katsuyoshi Uematsu M1 colloquium T. Park et al., Nature 440, 65 (2006) G. Knebel et al., PRB74, 020501 (2006)
Contents • Introduction • History of Superconductivity • Heavy Fermion (HF) system • Experiment • Motivation • Experimental method • Results of specific heat in CeRhIn5 • Summary • Future work
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
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.
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.
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
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
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
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.
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)
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)
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
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)
Experiment : Phase diagram T-H Phase Diagram of CeRhIn5 P = 2.41 (GPa) H = 0(T) 2.41 2.73GPa P = 2.73(GPa)
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.
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.
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 !!