1 / 31

Field-Induced Quantum Critical Point in CeCoIn 5

Field-Induced Quantum Critical Point in CeCoIn 5. J.Paglione et al,Phys.Rev.Lett. 91.246405 (2003) F. Ronning et al,Phys.Rev. B 71, 104528 (2005) Kitaoka Laboratory Takuya Fujii. Contents. Introduction - QCP - Heavy Fermion & Fermi Liquid Experimental Data

aurek
Télécharger la présentation

Field-Induced Quantum Critical Point in CeCoIn 5

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. Field-Induced Quantum Critical Point in CeCoIn5 J.Paglione et al,Phys.Rev.Lett. 91.246405 (2003) F. Ronninget al,Phys.Rev. B 71, 104528 (2005) KitaokaLaboratory Takuya Fujii

  2. Contents • Introduction - QCP - Heavy Fermion & Fermi Liquid • Experimental Data - Resistivity and specific heat of CeCoIn5 under fields - Phase diagram • Summary

  3. Metal Semiconductor Insulator Superconductor Material The ground states are changed ! Magnetism Physical properties around QCP Parameter Magnetic field(H) Material Pressure(P) Carrier doping

  4. High-Tc cuprates Heavy-fermionsystem QCP by carrier doping QCP by Pressure QCP (Quantum Critical Point): Phase transition of ground state (T=0K) (ex) magnetic order-disorder, normal phase-SC QCP (Quantum Critical Point) Unconventional SC around QCP

  5. Physical properties around QCP Non Fermi liquid Temperature (K) Magnetic fluctuations happen. magnetic order QCP Fermi Liquid 0 Parameters Physical properties around QCP are not described by Fermi Liquid theory.

  6. RKKY interaction conduction electron f-electron Heavy Fermion & Fermi Liquid <Heavy electron systems> f-electron: (RKKY interaction)  localize at the atom. (Kondo effect) 　  become itinerant by the hybridization between conduction electrons and f-electrons. localize : 局在する itinerant :遍歴した Kondo effect conduction electron rare earth ion Magnetic order Fermi liquid state by heavy electrons

  7. H // ab Normal SC H // c Crystalstructure of CeCoIn5 Tc=2.3K Heavy fermions superconductor • Tc=2.3 K at P=0. • C/T=350 mJ/mol K2 • H//abc2 ~ 11.8 T, H//cc2 ~ 5 T S. Ikeda et al., J. Phys. Soc. Jpn. 71 (2002) 1023.

  8. QCP of CeCoIn5 Comparison with isostructural CeRhIn5 isostructural AFM compound: CeRhIn5(TN=3.8K) CeCoIn5is in the vicinity of QCP at ambient pressure. M. Yashima et al.

  9. FL and NFL behavior Non Fermi-liquid 2D AFM r=r0+AT, C/T~ -log T 3D AFM r= r0+AT3/2, C/T=r0-aT1/2 Fermi-liquid (3D, 2D) r =r0+AT2 C/T=const A(slope): interaction between electrons

  10. Resistivity in high fields ( H // c) Temperature range of wider Hex Fermi liquid: A decreases as increasing field. By applying magnetic field, a FL regime is recovered !

  11. Field dependence of T2 coefficient • critical behavior • divergence close to H* (H*=5.1,α=-1.37)

  12. High-Hex C/T=const C/T=const Fermi liquid: Hex isclose to H* C/T~ -log T C/T~ -log T Non Fermi liquid: Specific heat in high fields ( H // c )

  13. H-T phase diagram H // c FL H* SC H* coincides with the critical field of SC Hc2(0).

  14. QCP in H // ab H // c H // ab Hc2ab~11.8 T Hc2c~5 T Cel/T= FLNFL was also observed around Hc2.

  15. ＋ H // ab ＋ ×Tc ●TFL H // c ＋Tc ＋ FL: H // c ○TFL FL: H // ab H-T phase diagram SC

  16. QCP SC FL QCP AF FL What is unique about CeCoIn5 ? comparison with YbRh2Si2 Hex approaches tocritical field value H＊ . critical behavior ! In CeCoIn5 : H＊Hc2(0) H-T phase diagram of YbRh2Si2 FL AF NFL T (K) H＊ SC FL 0 H(T) H＊ P.Gegenwart el et al. (2002)

  17. Summary • We observed a suppression of the non-Fermi liquid behaviors with increasing field, and the development of a Fermi liquid state. • It was a field-induced quantum critical point. • It coincides with the superconducting critical field Hc2(0).

  18. The end THE END

  19. FL: H // c H＊Hc2(0) FL: H // ab SC

  20. Motivation • Motivation Quantum critical behavior in the H-T phase diagram ? • Measurements Specific heat and resistivity in high magnetic field.

  21. QCP at negative P? - the QCP of CeCoIn5 under Pressure V.A.Sidorov et al. 2002

  22. ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Interaction ・ Fermi liquid ・ Fermi gas Heavy Fermion & Fermi Liquid No dynamic interaction between particles. Fermi gas : The interaction between electrons becomes very strong. itinerancy The electrons can’t move easily. The effective mass seems heavy. Fermi liquid : Heavy fermion is described by Fermi Liquid theory.

  23. QCP by the competition between RKKY interaction and Kondo effect

  24. - Resistivity of CeCoIn5under fields resistivity of metal at low temperature ( scattering by the phonon vibration) ( scattering between conduction electrons)

  25. - Resistivity of CeCoIn5under fields Tc NFL

  26. Resistivity of CeCoIn5under fields MR:magnetoresistance

  27. - Resistivity of CeCoIn5under fields Crossover from positive to negative MR T(K)=16 14.5 initial increase  an increase of spin disorder 13 a suppression of AF correlations 11.5 10 8.5 7 5.5 polarization of spins by increasing field strength a field-aligned state 4 T>Tc 2 0.1

  28. Hex : London penetration depth : Coherence length Hc2(//ab)=11.8T,(//c)=5T ab< c

  29. Non Fermi liquid behavior • The single-impurity multichannel Kondo model theory • Disorder-induced theory • Spin-fluctuation theory Non Femi-liquid 2D AFM r=r0+AT, C/T~ -log T 3D AFM r= r0+AT3/2, C/T=r0-aT1/2 Landau Fermi-liquid (3D, 2D) r =r0+AT2, C/T=const.c=const.

  30. NFL:near QCP,due to spin critical fluctuations, FL SC - H-T phase diagram of CeCoIn5

  31. H*

More Related