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A DFT (LDA+U) Study of the Electronic Properties of Square-Planar Coordinated

A DFT (LDA+U) Study of the Electronic Properties of Square-Planar Coordinated Copper Monoxide Structures. Paul M. Grant IBM Research Staff Member, Emeritus. Aging IBM Pensioner. Financial Support From: IBM Retiree Pension Fund Prior to 1990. MRS Spring Meeting

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A DFT (LDA+U) Study of the Electronic Properties of Square-Planar Coordinated

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  1. A DFT (LDA+U) Study of the Electronic Properties of Square-Planar Coordinated Copper Monoxide Structures Paul M. GrantIBM Research Staff Member, Emeritus Aging IBM Pensioner Financial Support From: IBM Retiree Pension Fund Prior to 1990 MRS Spring Meeting Moscone (West) Convention Center 25-29 April 2011, San Francisco, CA Session VV4.2 Room 2020 9:00 AM Tuesday, 26 April 2011

  2. Transition Metal Oxides “Should be Metals, But Aren’t” (Charge Transfer Insulators, Instead) After Imada, et al, RMP 70, 1039 (1998)‏

  3. TM O Cubic Rocksalt TMO a = b = c Cubic Rocksalt TMOs Direct and Reciprocal Lattices

  4. Cubic Rocksalt Divalent TMOs TMO 3d Config Properties MnO 5 MH-CTI (5.6) FeO 6 MH-CTI (5.9) CoO 7 MH-CTI (6.3) NiO 8 MH-CTI (6.5) CuO 9 XX Doesn't Exist! Why Not? See Imada, Fujimore, Tokura, RPM 70 (1988)‏

  5. Cu O Tenorite (Monoclinic CuO)‏

  6. DFT & (LDA + U)‏ • Implemented in LMTO by Anisimov, et al, JPCM 2, 3973 (1990)‏ • Applied to NiO, MnO, FeO, CoO and La2CuO4 • Plane-Wave Pseudopotential Implementation by Cococcioni and de Gironcoli, PRB 71, 035105 (2005)‏ • Applied to FeO and NiO • Download open-source package from http://www.pwscf.org Can Application of DFT (LDA+U) Help Unravel the Cubic Rocksalt CuO Enigma? …Let’s see…

  7. Tools • QUANTUM-ESPRESSO Suite of Codes • DFT (LDA+U) plus electron-phonon • Graphics by Tone Kolalj (XCrysDen) • www.quantum-espresso.org • “Dial-in” Parameters • G2 = 40 Ryρ = 320 Ry • Convergence ≤ 10-6Ry • “Smearing” = Methfessel-Paxton • Psuedopotentials: Ultrasoft, XC = Perdew-ZungerCu: 3d94s2 O: 2s22p4 • Hardware • 3.33 GHz Intel Core i7 – 12 GB+

  8. Rocksalt CuO Band Widths Note Degeneracies!

  9. Rocksalt CuO Fermiology (Combined) Note (Near) Degeneracies! Jahn-Teller Unstable? Alex M?

  10. Non-Magnetic Cubic Rocksalt CuO-- Electron-Phonon Properties -- α2F(ω) • λ ~ 0.6 – 0.7 • Other sc’s… σ = 0.04

  11. Proto-TMO AF-II Rocksalt [111]

  12. Proto-TMO AF-II Rocksalt [-1-1-1]

  13. LDA+U Calcs Grant, IOP-CS 129 (2008) 102042 The Answer(s) ! TMO Asymmetric Type II af-CuO Cell Tetragonal Distortion Siemons, et al, PRB 79 (2009) 195122

  14. References “Electronic Properties of Rocksalt Copper Monoxide,” APS MAR09-2008-006217, P. M. Grant, Pittsburgh (2009)

  15. “Non-Fermi Liquid”‘Nematic Fermi Fluids’ “Whatever!” “SDW”“NEEL”“A-F” “Whatever!” “Fermi Liquid”“Dilute Triplon Gas” “Whatever!” g*“QCP” “Insulator” “Conductor” ρlocal The Great Quantum Conundrum T g

  16. The Colossal Quantum Conundrum T “Real Metal”“Fermi Liquid” Superconductivity “Funny Metal”“Pseudogap”“Fond AF Memories” “Funny Metal”“Pseudogap”“Fond AF Memories” “SDW”“NEEL”“A-F” g*“QCP” “Insulator” “Conductor” g ρlocal • CuO Perovskites • Fe Pnictides • Bechgaard Salts

  17. n 0.00 +0.15 -0.15 3 6 U 0

  18. T “Real Metal”“Fermi Liquid” Superconductivity “Funny Metal”“Pseudogap”“Fond AF Memories” “SDW”“NEEL”“A-F” “Funny Metal”“Pseudogap”“Fond AF Memories” g* “Insulator” “Conductor” g The Colossal Quantum Conundrum U~U0 exp(-α g), g < g*;0,g > g* U = 3 U = 6 U = 0 Somewhere in here there has to be “BCS-like” pairing!

  19. Shakes or Spins or Both? Are They Copacetic, Competitive…or… …just another Conundrum? What formalism is the HTSC analogy to Migdal-Eliashberg-McMillan? (In other words, how do I calculate the value of the BCS gap?) • Generalized Linhard Response Function (RPA + fluctuations) Hu and O’Connell (PRB 1989) • Dielectric Response Function Kirznits, Maximov, Khomskii (JLTP 1972)

  20. Generalized Linhard Function HO (1989)

  21. Dielectric Response Function In principle, KMK can calculate the BCS gap for general “bosonic” fields, be they phonons, magnons, spin-ons, excitons, plasmons…or morons! KMK (1972)

  22. Other CuO Proxy Structures - Studies in Progress -

  23. 2.00 Å 5.226 Å 2 CuO segments per quadrant 16 Å between tubes Films & Tubes a = b = 3.905 Åc = 6 x 3.905 = 23.43 Å

  24. Films & TubesZones

  25. Films & TubesStates Landauer – Buettiger?

  26. Shakes & Spins Copacetic, Competitive or Conundrum? That is the question…anon • Bottom Line: • Can studying CuO proxies with DFT • + LDA+U • + phonons • provide the answer? • I say “Yes,” but… • Size Matters… • …and I need a… BIGGER COMPUTER! 3D phase diagram of overdoped La2-xCexCuO4 with 0.15 ≤ x ≤ 0.19. Pairing associated with quantum critical energy scales in superconducting electron-doped cuprates K. Jin, N. P. Butch, K. Kirshenbaum, J. Paglione, and R. L. Greene* -submitted to Nature- *will answer all questions…

  27. “Real Metal”“Fermi Liquid” “Superconductivity”

  28. n = +0.15 n = -0.15 Hubbard (eV) “Doping” (-e/CuO) U = 0 n = 0.00

  29. n = +0.15 n = -0.15 Hubbard (eV) “Doping” (-e/CuO) U = 3 n = 0.00

  30. Hubbard (eV) “Doping” (-e/CuO) U = 6 n = 0.00 n = +0.15 n = -0.15

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