Dynamical RVB: Cluster Dynamical Mean Field Studies of Doped Mott Insulators.

1. Dynamical RVB: Cluster Dynamical Mean Field Studies of Doped Mott Insulators. Statistical Mechanics Meeting Rutgers University December 17 2006 Gabriel Kotliar Rutgers Collaborators : G. Biroli M . Capone M Civelli K. Haule O. Parcollet T.D. Stanescu V. Kancharla A.M.Tremblay B. Kyung D. Senechal.

2. Outline • Anderson’s RVB framework. • (Cluster ) Dynamical Mean Field Theory • Optical conductivity and kinetic energy changes in the superconducting state.(K. Haule and GK) • Other results • Outlook

3. P. W. Anderson, Science235, 1196 (1987) • Doped quasi- 2d- spin ½ Mott insulator • t-J model , Hubbard model • High temperature superconductivity as a result of introducing holes in an RVB backround. • Anomalous properties result from doping a Mott insulating state.

4. t-J Hamiltonian Slave Boson Formulation: Baskaran Zhou Anderson (1987) Ruckenstein Hirschfeld and Appell (1987) b+i bi +f+si fsi = 1 Other RVB states with d wave symmetry. Flux phase or s+id ( G. Kotliar (1988) Affleck and Marston (1988) . Spectrum of excitation have point zeros like a a d –wave superconductor.

5. RVB phase diagram of the Cuprate Superconductors. Superexchange. • The approach to the Mott insulator renormalizes the kinetic energy Trvb increases. • The proximity to the Mott insulator reduce the charge stiffness , TBE goes to zero. • Superconducting dome. Pseudogap evolves continuously into the superconducting state. G. Kotliar and J. Liu Phys.Rev. B 38,5412 (1988) Related approach using wave functions:T. M. Rice group. Zhang et. al. Supercond Scie Tech 1, 36 (1998, Gross Joynt and Rice (1986) M. Randeria N. Trivedi , A. Paramenkanti PRL 87, 217002 (2001)

6. Cuprates: phase diagram Unusual Metal More conventional metal (FL?) “Pseudo-gap” Antiferromagnetic Mott Insulator superconductor Underdoped Overdoped Optimal doping

7. Problems with the approach. • Stability of the MFT. Ex. Neel order. Slave boson MFT with Neel order predicts AF AND SC. [Inui et.al. 1988] Giamarchi and L’huillier (1987). • Mean field is too uniform on the Fermi surface, in contradiction with ARPES.[Penetration depth, Wen and Lee ][Raman spectra, Photoemission ] • Description of the incoherent finite temperature regime. Development of DMFT in its plaquette version may solve some of these problems.!!

8. Dynamical Mean Field Theory. Cavity Construction.A. Georges and G. Kotliar PRB 45, 6479 (1992). A(w) 10

9. A(w) A. Georges, G. Kotliar (1992) 11

10. CLUSTER EXTENSIONS: umbiased reduction of the many body problem to a plaquette in a medium. Natural framework to formulate RVB. Can continue, metastable states. Reviews: Georges et.al. RMP(1996). Th. Maier, M. Jarrell, Th.Pruschke, M.H. Hettler RMP (2005); G. Kotliar S. Savrasov K. Haule O. Parcollet V. Udovenko and C. Marianetti RMP (2006) Tremblay Kyung Senechal cond-matt 0511334

11. Two Site Cellular DMFT (G.. Kotliar et.al. PRL (2001))in the 1D Hubbard modelM.Capone M.Civelli V. Kancharla C.Castellani and GK PRB 69,195105 (2004)T. D Stanescu and GK PRB (2006) U/t=4. 24

12. Order Parameter and Superconducting Gap do not scale for large U ! ED study in the SC state Capone et.al. (2006) Sarma et. al.

13. Optics and RESTRICTED SUM RULES Below energy Low energy sum rule can have T and doping dependence . For nearest neighbor it gives the kinetic energy. Use it to extract changes in KE in superconducing state

14. Optics and RESTRICTED SUM RULES <T>n is only defined for T> Tc, while <T>s exists only for T<Tc Experiment: use of this equation implies extrapolation. Theory : use of this equation implies of mean field picture to continue the normal state below Tc.

15. ~1eV Experiments interband transitions intraband Optical Conductivity Hubbard model U Excitations into upper Hubbard band • Kinetic energy in t-J model • Only moving of holes Drude t-J model J-t no-U

16. E Energy difference between the normal and superconducing state of the t-J model. K. Haule (2006)

17. . Spectral weight integrated up to 1 eV of the three BSCCO films. a) under-doped, Tc=70 K; b) ∼ optimally doped, Tc=80 K; c) overdoped, Tc=63 K; the fullsymbols are above Tc (integration from 0+), the open symbols below Tc, (integrationfrom 0, including th weight of the superfuid). H.J.A. Molegraaf et al., Science 295, 2239 (2002). A.F. Santander-Syro et al., Europhys. Lett. 62, 568 (2003). Cond-mat 0111539. G. Deutscher et. A. Santander-Syro and N. Bontemps. PRB 72, 092504(2005) . Recent review:

18. Where is the change of exchange energy? K. Haule (2006)

19. Finite temperature view of the phase diagram t-J model.K. Haule and GK (2006)

20. Doping Driven Mott transiton at low temperature, in 2d (U=16 t=1, t’=-.3 ) Hubbard model Spectral Function A(k,ω→0)= -1/π G(k, ω→0) vs k K.M. Shen et.al. 2004 Antinodal Region 2X2 CDMFT Senechal et.al PRL94 (2005) Nodal Region Civelli et.al. PRL 95 (2005)

21. Conclusions: Dynamical RVB • Captures the essential RVB physics. Slave boson method. • Solves many problems of the earlier RVB. • Allows the continuation of spin liquid states as metastable states. Functional of local spectral functions. • Nodal Antinodal dichotomy, emerges naturally. • Work in progress. No full solution of the eqs. is available yet.

22. Happy Birthday Elihu and Phil !

24. Pseudoparticle picture

25. How is the Mott insulatorapproached from the superconducting state ? Work in collaboration with M. Capone M Civelli O Parcollet

26. Nodal Antinodal Dichotomy and pseudogap. T. Stanescu and GK cond-matt 0508302

27. Superconducting DOS • = .06 d=.08 • = .1 d = .16 Superconductivity is destroyed by transfer of spectral weight. M. Capone et. al. Similar to slave bosons d wave RVB.

28. Superconductivity in the Hubbard model role of the Mott transition and influence of the super-exchange. ( work with M. Capone et.al V. Kancharla.et.al CDMFT+ED, 4+ 8 sites t’=0) .

29. cond-mat/0508205Anomalous superconductivity in doped Mott insulator:Order Parameter and Superconducting Gap . They scale together for small U, but not for large U. S. Kancharla M. Civelli M. Capone B. Kyung D. Senechal G. Kotliar andA.Tremblay. Cond mat 0508205M. Capone (2006).

30. M. Capone and GK cond-mat 0511334 . Competition fo superconductivity and antiferromagnetism.

31. Superconducting DOS • = .06 d=.08 • = .1 d = .16 Superconductivity is destroyed by transfer of spectral weight.. Similar to slave bosons d wave RVB. M. Capone et. al

32. Anomalous Self Energy. (from Capone et.al.) Notice the remarkable increase with decreasing doping! True superconducting pairing!! U=8t Significant Difference with Migdal-Eliashberg.

33. Mott Phenomeman and High Temperature Superconductivity Began Study of minimal model of a doped Mott insulator within plaquette Cellular DMFT • Rich Structure of the normal state and the interplay of the ordered phases. • Work needed to reach the same level of understanding of the single site DMFT solution. • A) Either that we will understand some qualitative aspects found in the experiment. In which case the next step LDA+CDMFT or GW+CDMFT could be then be used make realistic modelling of the various spectroscopies. • B) Or we do not, in which case other degrees of freedom, or inhomogeneities or long wavelength non Gaussian modes are essential as many authors have surmised. • Too early to tell, talk presented some evidence for A. .

39. Outline • Introduction. Mott physics and high temperature superconductivity. Early Ideas: slave boson mean field theory. Successes and Difficulties. • Dynamical Mean Field Theory approach and its cluster extensions. • Results for optical conductivity. • Anomalous superconductivity and normal state. • Future directions.

42. Temperature dependence of the spectral weight of CDMFT in normal state. Carbone et al, see also ortholani for CDMFT.

43. Larger frustration: t’=.9t U=16tn=.69 .92 .96 M. Civelli M. CaponeO. Parcollet and GK PRL (20050

44. . Spectral weight integrated up to 1 eV of the three BSCCO films. a) under-doped, Tc=70 K; b) ∼ optimally doped, Tc=80 K; c) overdoped, Tc=63 K; the fullsymbols are above Tc (integration from 0+), the open symbols below Tc, (integrationfrom 0, including th weight of the superfuid). H.J.A. Molegraaf et al., Science 295, 2239 (2002). A.F. Santander-Syro et al., Europhys. Lett. 62, 568 (2003). Cond-mat 0111539. G. Deutscher et. A. Santander-Syro and N. Bontemps. PRB 72, 092504(2005) . Recent review:

45. P.W. Anderson. Connection between high Tc and Mott physics. Science 235, 1196 (1987) • Connection between the anomalous normal state of a doped Mott insulator and high Tc. t-J limit. • Slave boson approach. <b> coherence order parameter. k, D singlet formation order parameters.Baskaran Zhou Anderson , (1987)Ruckenstein Hirshfeld and Appell (1987) .Uniform Solutions. S-wave superconductors. Uniform RVB states. Other RVB states with d wave symmetry. Flux phase or s+id ( G. Kotliar (1988) Affleck and Marston (1988) . Spectrum of excitation have point zerosUpon doping they become a d –wave superconductor. (Kotliar and Liu 1988). .

46. cluster in real space cluster in k space The simplest model of high Tc’s t-J, PW Anderson Hubbard-Stratonovich ->(to keep some out-of-cluster quantum fluctuations) BK Functional, Exact

47. Evolution of the spectral function at low frequency. If the k dependence of the self energy is weak, we expect to see contour lines corresponding to t(k) = const and a height increasing as we approach the Fermi surface.

49. DMFT Qualitative Phase diagram of a frustrated Hubbard model at integer filling T/W Georges et.al. RMP (1996) Kotliar Vollhardt Physics Today (2004)

50. Single site DMFT and kappa organics. Qualitative phase diagram Coherence incoherence crosover.