2 A DFT (LDA+U) Study of the Electronic Properties of Square-Planar Coordinated Copper Monoxide StructuresPaul M. Grant IBM Research Staff Member, EmeritusAging IBM PensionerFinancial Support From:IBM Retiree Pension Fund Prior to 1990MRS Spring MeetingMoscone (West) Convention Center25-29 April 2011, San Francisco, CASession VV4.2 Room 20209:00 AMTuesday, 26 April 2011222
3 Transition Metal Oxides “Should be Metals, But Aren’t” (Charge Transfer Insulators, Instead)After Imada, et al, RMP 70, 1039 (1998)3
4 Direct and Reciprocal Lattices Cubic Rocksalt TMOsDirect and Reciprocal LatticesTMOCubic Rocksalt TMOa = b = c
7 Can Application of DFT (LDA+U) Help Unravel the Cubic Rocksalt CuO Enigma? …Let’s see…DFT & (LDA + U)Implemented in LMTO by Anisimov, et al, JPCM 2, 3973 (1990)Applied to NiO, MnO, FeO, CoO and La2CuO4Plane-Wave Pseudopotential Implementation by Cococcioni and de Gironcoli, PRB 71, (2005)Applied to FeO and NiODownload open-source package from7
8 Tools QUANTUM-ESPRESSO Suite of Codes “Dial-in” Parameters Hardware DFT (LDA+U) plus electron-phononGraphics by Tone Kolalj (XCrysDen)“Dial-in” ParametersG2 = 40 Ry ρ = 320 RyConvergence ≤ 10-6 Ry“Smearing” = Methfessel-PaxtonPsuedopotentials: Ultrasoft, XC = Perdew-Zunger Cu: 3d94s2 O: 2s22p4Hardware3.33 GHz Intel Core i7 – 12 GB+
20 The Colossal Quantum Conundrum “Real Metal” “Fermi Liquid”“Funny Metal” “Pseudogap” “Fond AF Memories”Superconductivity“SDW” “NEEL” “A-F”Tgg*“Insulator”“Conductor”U~U0 exp(-α g), g < g*; 0, g > g*U = 3U = 6U = 0Somewhere in here there has to be “BCS-like” pairing!
21 Shakes or Spins or Both? …just another Conundrum? 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)
30 3D phase diagram of overdoped La2-xCexCuO4 with 0.15 ≤ x ≤ 0.19. Shakes & SpinsCopacetic, Competitive or Conundrum?That is the question…anon3D phase diagram of overdoped La2-xCexCuO4 with 0.15 ≤ x ≤ 0.19.Bottom Line:Can studying CuO proxies with DFT+ LDA+U+ phononsprovide the answer?I say “Yes,” but…Size Matters……and I need a… BIGGER COMPUTER!Pairing associated with quantum critical energy scales in superconducting electron-doped cupratesK. Jin, N. P. Butch, K. Kirshenbaum, J. Paglione, and R. L. Greene*-submitted to Nature-*will answer all questions…