2004: Room Temperature Superconductivity: Dream or Reality? 1972: High Temperature Superconductivity: Dream or Reality? Annual Review of Materials Science,

Slides:



Advertisements
Similar presentations
Anderson localization: from single particle to many body problems.
Advertisements

Quasiparticle Scattering in 2-D Helical Liquid arXiv: X. Zhou, C. Fang, W.-F. Tsai, J. P. Hu.
A new class of high temperature superconductors: “Iron pnictides” Belén Valenzuela Instituto de Ciencias Materiales de Madrid (ICMM-CSIC) In collaboration.
Iron pnictides: correlated multiorbital systems Belén Valenzuela Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC) ATOMS 2014, Bariloche Maria José.
Observation of a possible Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state in CeCoIn 5 Roman Movshovich Andrea Bianchi Los Alamos National Laboratory, MST-10.
Theory of the pairbreaking superconductor-metal transition in nanowires Talk online: sachdev.physics.harvard.edu Talk online: sachdev.physics.harvard.edu.
The “normal” state of layered dichalcogenides Arghya Taraphder Indian Institute of Technology Kharagpur Department of Physics and Centre for Theoretical.
Probing Superconductors using Point Contact Andreev Reflection Pratap Raychaudhuri Tata Institute of Fundamental Research Mumbai Collaborators: Gap anisotropy.
Recap: U(1) slave-boson formulation of t-J model and mean field theory Mean field phase diagram LabelStateχΔb IFermi liquid≠ 0= 0≠ 0 IISpin gap≠ 0 = 0.
Dynamical mean-field theory and the NRG as the impurity solver Rok Žitko Institute Jožef Stefan Ljubljana, Slovenia.
D-wave superconductivity induced by short-range antiferromagnetic correlations in the Kondo lattice systems Guang-Ming Zhang Dept. of Physics, Tsinghua.
Magnetism in 4d perovskite oxides Phillip Barton 05/28/10 MTRL 286G Final Presentation.
Physics “Advanced Electronic Structure” Lecture 3. Improvements of DFT Contents: 1. LDA+U. 2. LDA+DMFT. 3. Supplements: Self-interaction corrections,
Electronic structure of La2-xSrxCuO4 calculated by the
Superconducting transport  Superconducting model Hamiltonians:  Nambu formalism  Current through a N/S junction  Supercurrent in an atomic contact.
IRIDATES Bill Flaherty Materials 286K, UCSB Dec. 8 th, 2014.
Chaos and interactions in nano-size metallic grains: the competition between superconductivity and ferromagnetism Yoram Alhassid (Yale) Introduction Universal.
Quasiparticle anomalies near ferromagnetic instability A. A. Katanin A. P. Kampf V. Yu. Irkhin Stuttgart-Augsburg-Ekaterinburg 2004.
Semiconductors n D*n If T>0
Free electrons – or simple metals Isolated atom – or good insulator From Isolation to Interaction Rock Salt Sodium Electron (“Bloch”) waves Localised electrons.
Coordination Chemistry Bonding in transition-metal complexes.
Normal and superconducting states of  -(ET) 2 X organic superconductors S. Charfi-Kaddour Collaborators : D. Meddeb, S. Haddad, I. Sfar and R. Bennaceur.
Crystal Lattice Vibrations: Phonons
Superconductivity Characterized by- critical temperature T c - sudden loss of electrical resistance - expulsion of magnetic fields (Meissner Effect) Type.
Nematic Electron States in Orbital Band Systems Congjun Wu, UCSD Collaborator: Wei-cheng Lee, UCSD Feb, 2009, KITP, poster Reference: W. C. Lee and C.
Fluctuation conductivity of thin films and nanowires near a parallel-
Seillac, 31 May Spin-Orbital Entanglement and Violation of the Kanamori-Goodenough Rules Andrzej M. Oleś Max-Planck-Institut für Festkörperforschung,
Microscopic nematicity in iron superconductors Belén Valenzuela Instituto de Ciencias Materiales de Madrid (ICMM-CSIC) In collaboration with: Laura Fanfarillo.
Fundamentals and Future Applications of Na x CoO 2 W. J. Chang, 1 J.-Y. Lin, 2 C.-H. Hsu, 3 J.-M. Chen, 3 J.-M. Lee, 3 Y. K. Kuo, 4 H. L. Liu, 5 and J.
B. Valenzuela Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC)
Electronic instabilities Electron phonon BCS superconductor Localization in 1D - CDW Electron-electron (  ve exchange)d-wave superconductor Localization.
MgB2 Since 1973 the limiting transition temperature in conventional alloys and metals was 23K, first set by Nb3Ge, and then equaled by an Y-Pd-B-C compound.
Y. Tanaka Nagoya University, Japan Y. Asano Hokkaido University, Japan Y. Tanuma Akita University, Japan Alexander Golubov Twente University, The Netherlands.
@Nagoya U. Sept. 5, 2009 Naoto Nagaosa Department of Applied Physics
Dung-Hai Lee U.C. Berkeley Quantum state that never condenses Condense = develop some kind of order.
Pressure effect on electrical conductivity of Mott insulator “Ba 2 IrO 4 ” Shimizu lab. ORII Daisuke 1.
Entanglement Entropy in Holographic Superconductor Phase Transitions Rong-Gen Cai Institute of Theoretical Physics Chinese Academy of Sciences (April 17,
Fe As Nodal superconducting gap structure in superconductor BaFe 2 (As 0.7 P 0.3 ) 2 M-colloquium5 th October, 2011 Dulguun Tsendsuren Kitaoka Lab. Division.
Michael Browne 11/26/2007.
Zlatko Tesanovic, Johns Hopkins University o Iron-pnictide HTS are.
会社名など E. Bauer et al, Phys. Rev. Lett (2004) M. Yogi et al. Phys. Rev. Lett. 93, (2004) Kitaoka Laboratory Takuya Fujii Unconventional.
Sergey Savrasov Department of Physics, University of California, Davis Turning Band Insulators into Exotic Superconductors Xiangang Wan Nanjing University.
Unconventional superconductivity Author: Jure Kokalj Mentor: prof. dr. Peter Prelovšek.
Drude weight and optical conductivity of doped graphene Giovanni Vignale, University of Missouri-Columbia, DMR The frequency of long wavelength.
Fig.1. Schematic view of the Photoemission (top) and Inverse Photoemission (bottom) processes. Fig.2. PES and IPES spectra of polycrystalline silver, plotted.
Generalized Dynamical Mean - Field Theory for Strongly Correlated Systems E.Z.Kuchinskii 1, I.A. Nekrasov 1, M.V.Sadovskii 1,2 1 Institute for Electrophysics.
LIT-JINR Dubna and IFIN-HH Bucharest
Raman Scattering As a Probe of Unconventional Electron Dynamics in the Cuprates Raman Scattering As a Probe of Unconventional Electron Dynamics in the.
Spatially resolved quasiparticle tunneling spectroscopic studies of cuprate and iron-based high-temperature superconductors Nai-Chang Yeh, California Institute.
Three Discoveries in Underdoped Cuprates “Thermal metal” in non-SC YBCO Sutherland et al., cond-mat/ Giant Nernst effect Z. A. Xu et al., Nature.
Superconductivity with T c up to 4.5 K 3d 6 3d 5 Crystal field splitting Low-spin state:
Superconducting Cobaltites Nick Vence. Definition A material which looses its electrical resistivity below a certain temperature (Tc)is said to be superconducting.
Dirac fermions with zero effective mass in condensed matter: new perspectives Lara Benfatto* Centro Studi e Ricerche “Enrico Fermi” and University of Rome.
1 LDA+Gutzwiller Method for Correlated Electron Systems: Formalism and Its Applications Xi Dai Institute of Physics (IOP), CAS Beijing, China Collabrators:
Low-temperature properties of the t 2g 1 Mott insulators of the t 2g 1 Mott insulators Interatomic exchange-coupling constants by 2nd-order perturbation.
1 Non-uniform superconductivity in superconductor/ferromagnet nanostructures A. Buzdin Institut Universitaire de France, Paris and Condensed Matter Theory.
Lattice gauge theory treatment of Dirac semimetals at strong coupling Yasufumi Araki 1,2 1 Institute for Materials Research, Tohoku Univ. 2 Frontier Research.
A New Piece in The High T c Superconductivity Puzzle: Fe based Superconductors. Adriana Moreo Dept. of Physics and ORNL University of Tennessee, Knoxville,
Superconductivity Basics
Superconductivity and Superfluidity The Microscopic Origins of Superconductivity The story so far -what do we know about superconductors?: (i) Superconductors.
Evolution of the orbital Peierls state with doping
NTNU 2011 Dimer-superfluid phase in the attractive Extended Bose-Hubbard model with three-body constraint Kwai-Kong Ng Department of Physics Tunghai University,
Review on quantum criticality in metals and beyond
Bumsoo Kyung, Vasyl Hankevych, and André-Marie Tremblay
How might a Fermi surface die?
Phase structure of graphene from Hybrid Monte-Carlo simulations
UC Davis conference on electronic structure, June. 2009
Phases of Mott-Hubbard Bilayers Ref: Ribeiro et al, cond-mat/
Exotic magnetic states in two-dimensional organic superconductors
New Possibilities in Transition-metal oxide Heterostructures
Presentation transcript:

2004: Room Temperature Superconductivity: Dream or Reality? 1972: High Temperature Superconductivity: Dream or Reality? Annual Review of Materials Science, August 1972, Vol. 2, Pages Ginzburg V L, Kirzhnits D A (Eds) Problema Vysoko- temperaturnoi Sverkhprovodimosti (The Problem of High- Temperature Superconductivity) (Moscow: Nauka, 1977 ) [English Translation: High-Temperature Superconductivity (New York: Consultants Bureau, 1982)] 1977: Not If, When! ```` One can presume that the coming decade will be decisive for the problem of High- Temperature Superconductivity

Electronic Structure, Magnetism and Superconductivity in Na x CoO 2 Acknowledgements: D. Agterberg (UWM) A. Liebsch (Juelich) M.J. Mehl (NRL) D.A. Papaconstantopoulos (NRL) Igor Mazin, Michelle Johannes (Naval Research Laboratory) David Singh (ORNL) Instant superconductor: Just Add Water!

The Distorted Octahedral Environment of Co Ions NaCoO 2 : Co 3+ (3d 6 ) => band insulator CoO 2 : Co 4+ (3d 5 ) => Mott insulator? But Na x CoO 2 behaves almost oppositely… CoO 2 planes

Na content phase diagram 0 M, µ B 1 OBSERVED For x < 0.5, system is a simple metal For x > 0.5, system go through a sequence of magnetic metallic phases EXPECTED At x =0, system is a magnetic insulator At x=1, system is a band insulator For x < 0.5, system is a magnetic metal For x > 0.5, system is a simple metal Consistent overestimation of magnetism suggests spin fluctuations LDA typically finds smaller magnetic moments than experiment Exception: the vicinity of a quantum critical point

Multi-Orbital Nature of Fermi Surfaces Na 0.7 CoO 2 Two distinct Fermi surface types are predicted by calculation. a 1g = (xy) + (yz) + (zx) = 3z 2 -r 2 e g ’= (xy) + e  2  i/3 (yz) + e  4  i/3 (zx) Small pockets carry 70% of the weight in hydrated compound (Note that FS is 2D!)

Comparison with Experiment The large (a 1g )Fermi Surface is clearly seen by ARPES The smaller (e g ’) surfaces are absent M.Z. Hasan et al H. B. Yang et al WHY? Correlations beyond LDA Surface effects (relaxation, surface bands, Na content) Matrix elements

How does correlation affect the electronic structure? Strongly correlated systems are characterized by large U/t What is U in Na x CoO 2 ? LMTO: 3.7 eV (for all 5 d-bands) Narrow t 2g bands screened by Empty e g orbitals … U < 3.7eV (A.Liebsch) LDA+U: Corrects on-site Coulomb repulsion Gets good FS match for U= 4 eV (P. Zhang, PRL ) But U=4 eV > U C = 3eV for unobserved charge disproportionation ( K-W. Lee PRL ) For U<2.5 eV, small pockets remain Spin fluctuations: Renormalize bands, similarly to phonons Fermi surface is preserved, less weight

Optics: A Probe of Bulk Electronic Structure There are three basic peaks: . Peak shifts with changing Na content are reproduced. Peak heights and energy positions are exaggerated.   

Optics: Effect of LDA+U Application of LDA+U worsens agreement with experiment. Mott-Hubbard type correlation is not exhibited for any x!   How does electronic correlation manifest itself? 

Dynamical Correlation: DMFT Small e g ’ holes grow Some spectral weight shifts downward Dynamical Mean Field Theory gives a very different picture of correlation effects: LDA+U A.Liebsch, ‘05

Summary of Part I Na x CoO 2 has an unusual magnetic phase diagram The system does not behave as a Mott-Hubbard insulator, despite a rather narrow t 2g bandwidth The LDA+U method worsens agreement with optical measurements Dynamical correlations show weight transfer from a 1g  e g i.e. holes grow! Calculations, in conjunction with experiment, suggest the presence of spin fluctuations

Part II: Superconductivity What kind of superconductor is Na 0.35 CoO 2  yH 2 O ? Pairing state: Singlet? Triplet? Order parameter: s,p,d,f …?

Experimental evidence for pairing state...singlet order parameter with s-wave symmetry is realized in NaxCoO2.yH2O - JPSJ 72, 2453 (2003)...an unconventional superconducting symmetry with line nodes - cond-mat/ (2004) Unconventional superconductivity in NaxCoO2 yH2O - cond- mat/ (2004) Possible singlet to triplet pairing transition in NaxCoO2 H2O - PR B70, (2005) Possible unconventional super- conductivity in NaxCoO2.yH(2)O probed by muon spin rotation and relaxation - PR B70, (2005) Evidence of nodal superconductivity in Na0.35CoO H2O - PR B71, (2005)...magnetic fluctuations play an important role in the occurrence of superconductivity - JPSJ 74, 867 (2005) Our results make superconducting NaxCoO2 a clear candidate for magnetically mediated pairing - cond-mat/ (2005) … superconducting electron pairs are in the singlet state - JPSJ 74 (2005)

» Superconducting state not fully gapped What pairing states can we exclude? » No states with L≠ 0 » k z -dependent order parameter unphysical After Sigrist and Ueda RMP (1991) 9 representations 25 total states  SR No static magnetic moments » No states with L  0 » No non-unitary triplet states Two dimensionality c/a ratio ~ 3.5  ab /  c ~ 10 3 » k z -dependent order parameter unrealistic DOS Probes Non-exponential decay of C/T vs. T No coherence peak in 1/T 1 Non-exponential decay of relaxation time » Superconducting state not fully gapped

How can pairing state be further resolved? f states Presently, results are contradictory All remaining states are triplet f Both f states are axial Knight Shift can distinguish: Spin direction is  to vector order parameter KS constant across T C for planar spins (axial order parameter) KS decreases across T C for axial spins (planar order parameter)

Evidence of Spin Fluctuations in Na 0.35 CoO 2  1.4H 2 O Curie-Weiss like behavior of 1/T 1 (above T C ), with negative  Correlation of T C with magnetic fluctuations as measured by NQR Direct neutron observation of spin fluctuations in related compounds LDA calculations indicate proximity to quantum critical point There is growing evidence that SF have a role in the superconductivity: Details of pairing/pair-breaking in a particular system depend on: i) Fermiology ii) spin fluctuation spectrum - Im  (q,  )

Is pairing interaction always attractive? Consider BCS formula (in this notation, attractive V>0): If  k  and  q  are of the same sign, V must be positive. But if they are of the opposite sign, the corresponding V can be negative (repulsive) and still be pairing! 17 Charge fluctuations are attractive regardless of parity (V>0) Spin fluctuations are repulsive (V<0) in a singlet channel (BCS, HTSC) Spin fluctuations are attractive (V<0) in a triplet channel (He 3, Sr 2 RuO 4 ?)

Spin fluctuations in Na x CoO 2 yH 2 O AD=G/2 AC=AB=G/4 Im  0 (q,  )/  |  0 Re  0 (q,0)   (q,  =  k f(  k+q ) - f(  k )  k+q -  k -  - i   (q,    (q,  1- I(q,  ) For a Mott-Hubbard system, I(q,  ) is main factor For Na x CoO 2 yH 2 O, we expect peaks to come from non-interacting part:

Primary nesting SF’s are pair breaking for every state The secondary-nesting SF are either pair-breaking (s) or mutually canceling (d,p) Spin fluctuations: pairing and pair-breaking  k  = V kq,   q  F(  q ,T)  qq V<0 V>0  k  = V kq,   q  F(  q ,T)  qq V>0

Odd gap superconductivity  (  )= -  ( -  ) Now spatial+spin Pauli principle for a pair is reversed: (Berezinskii, ‘74 … Balatsky et al, ‘92

What to expect from a triplet s-wave superconductor Severely reduced Hebel-Slichter peak - by at least (T c /E F ) 2 Impurities should have small effect on T c Finite DOS even at T=0 (gapless) - noexponential thermodynamics Vanishing of pair tunneling in even-odd Josephson junction

Summary of Part II Calculated spin fluctuations are compatible only with odd gap, triplet superconductivity - this is consistent with experiment so far. The current body of experimental evidence strongly suggests unconventional superconductivity Both experiment and calculation point to the presence of spin fluctuations, possibly connected to the superconductivity

NQR, Fujimoto et al C/T, Lorenz et al  SR, Kanigel et al, Knight, Higemoto et alAbsence of mag. fields, Higemoto et al Hc2, Maska et al Superconductivity: symmetry (experiment)