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A DFT (LDA+U) Study of the Electronic Properties of Square-Planar Coordinated Copper Monoxide Structures Paul M. Grant IBM Research Staff Member, Emeritus.

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Presentation on theme: "A DFT (LDA+U) Study of the Electronic Properties of Square-Planar Coordinated Copper Monoxide Structures Paul M. Grant IBM Research Staff Member, Emeritus."— Presentation transcript:

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2 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 Moscone (West) Convention Center April 2011, San Francisco, CA Session VV4.2 Room :00 AM Tuesday, 26 April 2011

3 Transition Metal Oxides Should be Metals, But Arent (Charge Transfer Insulators, Instead) After Imada, et al, RMP 70, 1039 (1998)

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

5 Cubic Rocksalt Divalent TMOs TMO3d Config Properties MnO 5 MH-CTI (5.6) FeO6 MH-CTI (5.9) CoO7 MH-CTI (6.3) NiO8 MH-CTI (6.5) CuO9 XX Doesn't Exist! See Imada, Fujimore, Tokura, RPM 70 (1988) Why Not?

6 Tenorite (Monoclinic CuO) Cu O

7 DFT & (LDA + U) Implemented in LMTO by Anisimov, et al, JPCM 2, 3973 (1990) Applied to NiO, MnO, FeO, CoO and La 2 CuO 4 Plane-Wave Pseudopotential Implementation by Cococcioni and de Gironcoli, PRB 71, (2005) Applied to FeO and NiO Download open-source package from Can Application of DFT (LDA+U) Help Unravel the Cubic Rocksalt CuO Enigma? …Lets see…

8 Tools QUANTUM-ESPRESSO Suite of Codes DFT (LDA+U) plus electron-phonon Graphics by Tone Kolalj (XCrysDen) Dial-in Parameters G 2 = 40 Ryρ = 320 Ry Convergence Ry Smearing = Methfessel-Paxton Psuedopotentials: Ultrasoft, XC = Perdew-Zunger Cu: 3d 9 4s 2 O: 2s 2 2p 4 Hardware 3.33 GHz Intel Core i7 – 12 GB+

9 Rocksalt CuO Band Widths Note Degeneracies!

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

11 Non-Magnetic Cubic Rocksalt CuO -- Electron-Phonon Properties -- λ ~ 0.6 – 0.7 Other scs… α 2 F(ω) σ = 0.04 T C (K) λμ*μ* K 3 C Rb 3 C Cs 3 C

12 Proto-TMO AF-II Rocksalt [111]

13 Proto-TMO AF-II Rocksalt [ ]

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

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16 References Electronic Properties of Rocksalt Copper Monoxide, APS MAR , P. M. Grant, Pittsburgh (2009)

17 Non-Fermi Liquid Nematic Fermi Fluids Whatever! Fermi Liquid Dilute Triplon Gas Whatever! SDW NEEL A-F Whatever! T g g* QCP InsulatorConductor ρ local The Great Quantum Conundrum

18 Real Metal Fermi Liquid Funny Metal Pseudogap Fond AF Memories SDW NEEL A-F Superconductivity T g g* QCP InsulatorConductor ρ local Funny Metal Pseudogap Fond AF Memories The Colossal Quantum Conundrum CuO Perovskites Fe Pnictides Bechgaard Salts

19 n U

20 Real Metal Fermi Liquid Funny Metal Pseudogap Fond AF Memories Superconductivity SDW NEEL A-F T g g* InsulatorConductor Funny Metal Pseudogap Fond AF Memories The Colossal Quantum Conundrum U~U 0 exp(-α g ), g g* Somewhere in here there has to be BCS-like pairing! U = 6 U = 0 U = 3

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

22 Generalized Linhard Function HO (1989)

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

24 Other CuO Proxy Structures - Studies in Progress -

25 Films & Tubes a = b = Å c = 6 x = Å Å 2.00 Å 2 CuO segments per quadrant 16 Å between tubes

26 Films & Tubes Zones

27 Films & Tubes States Landauer – Buettiger?

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30 Shakes & Spins Copacetic, Competitive or Conundrum? That is the question…anon 3D phase diagram of overdoped La2-xCexCuO4 with 0.15 x 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… 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!

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32 Superconductivity Real Metal Fermi Liquid

33 U = 0n = 0.00 n = n = Hubbard (eV)Doping (-e/CuO)

34 U = 3n = 0.00 Hubbard (eV)Doping (-e/CuO) n = n = -0.15

35 U = 6n = 0.00 n = n = Hubbard (eV)Doping (-e/CuO)


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