Organic Superconductivity P. M. Chaikin, Center for Soft Matter Research, NYU Brief History A Remarkable Set of Materials! Nature of the Superconducting State? The Discovery of New Condensed Phases & New Effects in High Magnetic Fields October 12, 2007 (TMTSF)2PF6 the first organic superconductor Controllable 6 Coherence? Triplet? 2K 4 1K BCS@50 2 V/K) μ 0 N( 2μH= Δ -2 -2L -4 -1L c' 1L -50 -40 -30 -20 -10 0 10 20 30 40 50 θ (TMTSF)2 PF6 - Most Remarkable Electronic Material Ever Discovered So far in one single crystal: All the usual competitions: Metal-Insulator, Magnetic-Superconductor, Commensurate-Incommensurate, FermiLiquid- NonFermiLiquid, Spin Density Wave - Charge Density Wave…… October 12, 2007 Exhibits all transport mechanisms known to man: Metallic, Sliding Density Wave, Superconducting, Quantum Hall BCS@50 Plus somethings new : Field Induced SDW/QHE Giant Nernst Effect, Magic Angle Effects Triplet Superconductivity, Field Induced Slabs Who’s to Blame Princeton • InJae Lee (Chonbuk National University) • Weida Wu (Rutgers) UCLA • Stuart Brown • Gil Clark • David Chow Boston College • Mike Naughton With Advice from: Andrei Lebed, Victor Yakovenko, Phil Anderson, David Huse, Phuan Ong Superconductivity Discovered by 1911 Gilles Holst Superconductivity Explained 1957 BCS Bill Little proposes Excitonic, 1963 Organic, Polymeric Superconductor Schegolev, Bloch, Heeger,…. Fred Wudl discovers TTF Work on “1D” metals, TCNQ’s 1970 TTF-TCNQ first organic metal 1973 Alan Heeger, (not superconductor) others Rick Greene, (SN)x , first (and only) 1975 polymeric superconductor Tc~0.3K Bechgaard and Jerome First Organic 1979 Superconductor TMTSF2 PF6 Tc~1.2K G. Saito, (ET)2Cu[N(CN)2Br] Tc~13K Superconductivity Discovered by 1911 Gilles Holst Superconductivity Explained 1957 BCS Bill Little proposes Excitonic, 1963 Organic, Polymeric Superconductor Schegolev, Bloch, Heeger,…. Fred Wudl discovers TTF Work on “1D” metals, TCNQ’s 1970 TTF-TCNQ first organic metal 1973 Alan Heeger, (not superconductor) others Rick Greene, (SN)x , first (and only) 1975 polymeric superconductor Tc~0.3K Bechgaard and Jerome First Organic 1979 Superconductor TMTSF2 PF6 Tc~1.2K G. Saito, (ET)2Cu[N(CN)2Br] Tc~13K “g-ology Phase Diagram 1D electrons g 1 kF -kF g2 2kF kF-q kF Only two interactions important q = 2kF ε ε backscattering forward scattering -kF kF -kF kF g1(q=2kF) g2(q=0) Superconductivity Discovered by 1911 Gilles Holst Superconductivity Explained 1957 BCS Bill Little proposes Excitonic, 1963 Organic, Polymeric Superconductor Schegolev, Bloch, Heeger,…. Fred Wudl discovers TTF Work on “1D” metals, TCNQ’s 1970 TTF-TCNQ first organic metal 1973 Alan Heeger, (not superconductor) others Rick Greene, (SN)x , first (and only) 1975 polymeric superconductor Tc~0.3K Bechgaard and Jerome First Organic 1979 Superconductor TMTSF2 PF6 Tc~1.2K G. Saito, (ET)2Cu[N(CN)2Br] Tc~13K R R X X Y2 X X Y1 X X X X X X X X R R Y2 Y1 DBTTF : X=S R R TTF : X=S, R=H DBTSF : X=Se X X TSF : X=Se, R=H ET(BEDT-TTF) : X=Y1=Y2=S TTeF : X=Te, R=H BO(BEDO-TTF) : X=S,Y1=Y2=O X X Wudl TMTSF : X=Se, R=Me BETS(BEDT-TSF) : X=Se,Y1=Y2=S TMTTF : X=S, R=Me EOET : X=S,Y =S,Y =O X X 1 2 X X R R HMTTF : X=S HMTSF : X=Se X X S S S S HMTTeF : X=Te TTF : X=S, R=H Quasi 1D S S X X S S S S S S TSF : X=Se, R=H OMTTF : X=S BPDT-TTF OMTSF : X=Se S S S S TTeF : X=Te, R=H S S S S BVDT-TTF Me Me TMTSF : X=Se, R=Me S S S S Te Te S S TMTTF : X=S, R=Me BMDT-TTF Te Te S S S Me Me S S S S S S BDMT-TTeF BET-TTF S S S XX XC H MDT-TTF H2n+1CnX S S n 2n+1 Y Y R2 R1 2 X X 1 S S H2n+1CnX XCnH2n+1 XX R2 R1 TTCn-TTF : X=S R R XX TSeCn-TTF : X=Se TTeC -TTF : X=Te X X DMTTA : X=S, R1=H, R2=Me n Y Y TMTTA : X=S, R1=R2==Me 2 1 R R S C H 6,7-DMTTA : X=S, R1=H, R2=Me S S n 2n+1 XX TSA : X=Se, R1=R2=H TTN : X=S, R=H DMTSA : X=Se, R1=Me, R2=H S S S CnH2n+1 TSN : X=Se, R=H 6,7-DMTSA : X=Se, R1=H, R2=Me CnTET-TTF ET(BEDT-TTF) : X=Y1=Y2=S TMTTeN : X=Te, R=Me TMTSA : X=Se, R1=R2=Me DMTTeA : X=Te, R1=Me, R2=H BO(BEDO-TTF) : X=S,Y1=Y2=O S S BETS(BEDT-TSF) : X=Se,Y =Y =S XX R1 S 1 2 R R4 R1 2 S EOET : X=S,Y1=S,Y2=O R R 3 2 DTPY : R =R =H YY 1 2 S MSDTPY : R1=SeMe,R2=H S TTT : X=Y=S, R1=R2=R3=R4=H MTDTPY : R =SMe,R =H S 1 2 S Yagubski F2TTT : X=Y=S, R1=R2=R3=R4=H R Quasi 2D 2 Ph2DTPY : R1=Ph,R2=H TST : X=Y=Se, R1=R2=F, R3=R4=H R 3,8-(MeO)2DTPY : R1=H, R2=MeO TTeT : X=Y=Te,R1=R2=R3=R4=H 1 ETDTPY Saito Me2N NMe2 S Me S S Me2N NMe2 Me N NMe 2 2 S S Me S TMPD TDAE TMDTDM-TTF Superconductivity Discovered by 1911 Gilles Holst Superconductivity Explained 1957 BCS Bill Little proposes Excitonic, 1963 Organic, Polymeric Superconductor Schegolev, Bloch, Heeger,…. Fred Wudl discovers TTF Work on “1D” metals, TCNQ’s 1970 TTF-TCNQ first organic metal 1973 Alan Heeger, (not superconductor) others Rick Greene, (SN)x , first (and only) 1975 polymeric superconductor Tc~0.3K Bechgaard and Jerome First Organic 1979 Superconductor TMTSF2 PF6 Tc~1.2K G. Saito, (ET)2Cu[N(CN)2Br] Tc~13K Observed and hinted at ground states BEDT-TTF family (TMTSF)2PF6 Supercond – singlet Supercond – triplet? - d-wave? SDW - LOFF? CDW Ferromagnetic Field Induced SDW SDW Quantum Hall CDW Fermi-Liquid Quantum Hall? Non – Fermi, Luttinger? Liq Fermi-Liquid Mott Insulator? Crystal Structure of Bechgaard Salts (TMTSF)2X • Highly anisotropic -2 -5 σa : σb : σc = 1 : 10 : 10 4t : 4t : 4t = 1 : 0.1: 0.003 (eV) a b c 2 σi ~ ti • Good metal ρ ~1 μΩcm at 4K (ρ (Cu) ~ 1μΩcm at 300K). c b • Extremely clean a l~10μ at 1K, h/τ~0.1K at 1K Triclinic • ¼ Filled, Slightly Dimerized α =°=°=°83.39 ,βγ 86.27 , 71.01 Single chain has charge gap. oo o abc=Α=Α=Α7.297 , 7.711 , 13.522 Phase Diagram (TMTSF) 2 PF 6 15 metal 10 Woowon T(K) S D W 5 Kang S D m 0 W e ta 0 F l I n = S 0 5 sc D P Q W (k b a r) H 10 E m et al 15 0 5 10 15 20 25 30 H(tesla) 1D metals are unstable – Fermi Surfaces Nest Interchain hopping – warped Fermi Surface – regain metal Pressure increases interchain hopping – more 3D 15 metal 10 T(K) S D W 5 S D m e 0 W ta 0 F l I n = M S 0 or 5 sc D e P Q W (k b 3 a D r) H 10 li E k e m et al 15 0 5 10 15 20 25 30 H(tesla) 3D (P,H,T) phase diagram of (TMTSF)2PF6 First guess from g-ology g1 TS SDW ) (SS) K ( g2 T SDW is - ax P(kb / c ar) SC H / 1D-electron gas phase diagram Insulator-Superconductor Bechgaard, Jerome 1979 (“g-ology”). J. Solyom, Adv. Phys 28, 201 (1979) Singlet or Triplet ? Radiation damage experiments Resistive upper critical fields Hp =16 KG Non s-wave Singlet (s,d-wave)? M.Y. Choi et.al., Phys. Rev. B25, 6208 (1982) P.M. Chaikin, M.Y. Choi and R.L. Greene, Mag. Mat. 31, 1268 (1983) Proton spin-lattice relaxation experiments M. Takigawa et.al., J.Phys. Soc. Jpn. 56, 873 (1987) T3 Non S-wave (line node on FS) Belin et. al. Thermal conductivity S-wave (a finite gap) (No node on FS) Singlet – Triplet Unresolved after ~ 12 years in 1980’s But People discovered unusual things in Magnetic Fields Electron Orbits for a Magnetic Field along c H One-Dimensionalized by Magnetic field k space Real Space ⎛ 4t ⎞ ⎜ b ⎟ wb = ⎜ b ⎟ ev⎝ F B z⎠ vF y h B λ = z x ebB z evf Bbz ωb = ky h Chaikin, Azbel, Holstein, ‘83 kx But nesting at q=2kF +/- nG, G=2π/λ Woowon Kang Integer Quantum Hall Effect in (TMTSF)2PF 6 100 T = 300mK N = 1 P = 10kbar ) Ω 50 (m N = 2 xy R N = 3 N = 4 0 60 ) Ω (m xx 30 R 0 0 5 10 15 B(tesla) 15 metal 10 T(K) S D W 5 S D m e 0 W ta 0 F l I n = M S 0 or 5 sc D e P Q W (k b 3 a D r) H 10 li E k e m et al 15 0 5 10 15 20 25 30 H(tesla) More 1D like Main lesson: Magnetic field perpendicular to the chains reduces electronic dimension Does this decouple chains/planes? H=0 c b c b H a 3D coherent Coherent planes Two Contributions to Magnetic Critical Field - Orbital and Spin Orbital term derives from Field Expulsion Spin derives from susceptibility e.g.