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S. Haddad LPMC, Département de Physique, Faculté des Sciences de Tunis, Tunisia S. Charfi-Kaddour

Interplay between SDW and superconductivity in the quasi-one organic superconductor (TMTSF) 2 ClO 4. S. Haddad LPMC, Département de Physique, Faculté des Sciences de Tunis, Tunisia S. Charfi-Kaddour LPMC, Faculté des Sciences de Tunis, Tunisia M. Héritier

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S. Haddad LPMC, Département de Physique, Faculté des Sciences de Tunis, Tunisia S. Charfi-Kaddour

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  1. Interplay between SDW and superconductivity in the quasi-one organic superconductor (TMTSF)2ClO4 S. Haddad LPMC, Département de Physique, Faculté des Sciences de Tunis, Tunisia S. Charfi-Kaddour LPMC, Faculté des Sciences de Tunis, Tunisia M. Héritier LPS, Orsay, (unité mixte de Recherche) CNRS-Paris XI, France R. Bennaceur LPMC, Faculté des Sciences de Tunis, Tunisia

  2. Acknowledgments Theory Experiments C. Bourbonnais (Sherbrooke)D. Jérome (Orsay) A. G. Lebed (Arizona) Y.Maeno (Kyoto) N. Joo (Orsay)

  3. Why quasi-one organic superconductors? • (TMTSF)2ClO4: an exotic organic conductor • Effect of disorder on the interplay between Superconductivity and SDW • Effect of a magnetic field: new field induced SDW (FISDW) phases

  4. IRM Accelerator LHC (CERN) Maglev in Japan: fast, safe and economic Why superconductors ? Uses for superconductors: • Also as … • Electric generator (99% more efficient than ordinary one) • SQUID (Superconducting Quantum Interference Device): sensing weak magnetic field • Military: antenna and in detecting mines (US NAVY) …

  5. The future of Superconductors

  6. Little’s Proposition(1964): look for organic conductors with one dimensional character to get high Tc !!! Why organic superconductors ? Dream: towards room temperature superconductors !!! Problems:difficulties to synthesize such materialsuntil…

  7. BUT : TC=1.2 K (so low !!!) a complete laboratory for physicists intensive study SDW SC Why organic superconductors ? • 1979:discovery of organic superconductivity in a quasi-one dimensional salt (TMTSF)2PF6(D. Jérome’s group) …then in Bechgaard salts denoted by (TMTSF)2X (X=PF6-, ClO4-…) But:there are still open questions !!! Interplay between SC/ SDW: coexistence or competition?

  8. TMTSF X TMTSF=tétraméthyl-tétraséléna-fulvalèneX= anion: Br-, PF6-; ClO4-… Needle like c a b Crystal structure of(TMTSF)2X

  9. t’b Conducting planes tb ta c tc « tb« tasc «sb« saquasi-1D conductors tc b a Organic chains of TMTSF molecules Key parameters of(TMTSF)2X

  10. 1D LL 2D FL AF SC T. Vuletic, et al. Eur. Phys. J. B 25, 319 (2002) ClO4 (TMTSF)2ClO4is superconducting at ambient pressure (Tc= 1.2 K) Phase diagram of Bechgaard salts

  11. TMTSF c ClO4 a b 2 possible orientations or (TMTSF)2ClO4 : What makes it so special ? ClO4 anions are noncentrosymmetric

  12. Periodic potential: V (y) =V cos( /b y) V: anion potential Anion ordering in (TMTSF)2ClO4 t b c Rapidly cooled sample (quenched): ClO4 anionsdisordered ! V = 0 ClO4 TMTSF b (TMTSF)2ClO4 : anion ordering Slowly cooled sample (relaxed): ClO4 anions order along b direction at TAO = 24 K

  13. Dispersion relation of relaxed (TMTSF)2ClO4 Two-band energy spectrum k ┴ Fermi surface of (TMTSF)2ClO4 2V k B B A A Fermi surface of (TMTSF)2X without anion ordering

  14. Puzzles !!! SDW SC Joo et al.,Euro. Phys. Lett. 72, 645 (2005) Effect of cooling rate relaxed samples (slowly cooled) : Superconducting (SC) For the intermediate cooling rate: both SCand magnetism. In the quenched samples: pure magnetic state (SDW)

  15. effect of cooling rate: generic phase diagram T metal TSDW Pure SDW TSC SC/ SDW Pure SC Cooling rate

  16. Anion ordering two band energy spectrum e(k) A B kFA k kFB Eg Model :Interplay of superconductivity and magnetic phases Bands separated by gap Eg

  17. system set of coupled chains Eg tb Method: perturbative renormalization group theory (Bourbonnais et al.) SDW CDW singlet superconductivity (SSc) triplet superconductivity(tSc)

  18. Most divergent the most dominant fluctuation. Scattering processes: (g-ology model) g(1) processes g(2) processes m m m m m m m m m m m m m m m m m m m m

  19. Eg= 15 K Eg= 8 K Intermediate cooling Slow cooling Eg = 5 K Rapid cooling Scaling flows of the most divergent tb = 300 K, EF = 2000 K, Tcross= 170 K, = 0.6 Coexisting singlet SC/SDW Singlet SC Pure SDW

  20. pure singlet SC (SCs) phase (SCs + SDW) pure SDW Cooling rate S. Haddad et al. to appear in J. Low Temp. Phys. Phase diagram Limits RG calculations: Is there coexistence or segregation between SC and SDW ?

  21. SC SC SDW SC Disordered ClO4 region Ordered ClO4 region decrease cooling rate (decrease disorder) Experiments Phase segregation ! Next step:compare free energies (pure SC, pure SDW, SC+SDW)

  22. H c b a Organic chains Cascade of field-induced SDW (FISDW) phases Effect of a transverse magnetic field

  23. Temperature field phase diagram in the (TMTSF)2ClO4 (Chung et al. 2000) SDW I ? SDW III ? ? SDW II SDW IV Ok-Hee Chung et al., PRB 61 (2000) Other puzzle: Effect of a high magnetic field Generic Temperature field phase diagram in the absence of anion ordering: 10 8 metal 6 Temperature (K) 4 N=0 2 N=1 2 3 5 10 15 20 25 Magnetic field (T) Cascade of FISDW phases :already explained within the Quantized nesting model (Lebed, Gor’kov, Maki, Héritier, Montambaux, Lederer). SDW phase inside an original SDW state !!!

  24. Focus on N=0 and N=1 phases High field phases correspond lowest N values 10 8 metal 6 Temperature (K) 4 N=0 2 N=1 2 3 5 10 15 20 25 Magnetic field (T)

  25. In the presence of magnetic field: effective anion gap G=eHb/hc, binterchain distance

  26. Osada et al. (Phys. Rev. Lett. 1992) Intraband nesting: N=0 phase Interband nesting: N=1 phase N=0 Tow nesting vectors N=1 one nesting vector e(k) A A B B q1 D D k k

  27. N=0 FISDW phase:Generalized Stoner Criterion Intraband term Term describing the overlap of the tow SDW components appearing on the two bands Instability criteria MFT + RG N=1 FISDW phase:standard Stoner Criterion

  28. F T*1 T0 T1 T F0 F1 Thermodynamics:Competition between the N=0 and the N=1 phase

  29. ? ? ? Experiments (Chung et al. 2000) Our model S. Haddad et al. Phys. Rev. Lett., 89, 087001 (2002) S. Haddad et al. Phys. Rev B, 72, 085104 (2005) Temperature-field phase diagram

  30. c H Free of bird flu ! b a a Organic chains b Confinement in the (a,b) plane Effect of a parallel magnetic field

  31. Experiment (Danner et al. 1997) Our model submitted to Eur. Phys. J. B Joo et al. 2006

  32. Quantum mechanical calculation Layer index

  33. Other models in competition with our !!! Probability in transverse direction A. G. Lebed, Phys. Rev. Lett. (2005) Index layer But, does not explain the resistance behavior

  34. SDW Sc What should be next ? • symmetry of the gap in(TMTSF)2ClO4? triplet or singlet ? • Interplay between SuperconductivityandSDW : coexistence or competition ? • References • N. Matsunaga et al. J. Low Temp. Phys. 117, 1735 (1999) • J. Greer et al. Physica C 400, 59 (2003) • N. Joo et al., cond-mat/0507641 • S. K. McKernan et al., P.R.L 75, 1630 (1995) • O. H. Chung et al., P.R.B 61, 11649 (2000) • J. Moser, Ph. D. thesis, Orsay (France) (1999) (unpublished) • C. Bourbonnais and L. G. Caron, Int. J. Mod. Phys. B, 5, 1033 (1991) • J. Kishine and K. Yonemitsu, J. Phys. Soc. Jpn. 67, 1714 (1998) • T. Osada et al. P.R.L. 77, 5261 (1996) • S. Uji et al., P.R.B 53, 14399 (1996) • H. Yoshino et al., Synth. Met. 133-134, 55 (2003) • H. I. Ha et al., cond-mat/0503649 • G. Lebed et al., P.R.L. 93, 157006 (2004) • A.G. Lebed and P. Bak, P.R.B 40, R11433 (1989) • T. Osada et al., P.R.L. 69, 1117 (1992) • S. Haddad et al., P.R.B 72, 085104 (2005)

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