2A 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
3Transition Metal Oxides “Should be Metals, But Aren’t” (Charge Transfer Insulators, Instead)After Imada, et al, RMP 70, 1039 (1998)3
4Direct and Reciprocal Lattices Cubic Rocksalt TMOsDirect and Reciprocal LatticesTMOCubic Rocksalt TMOa = b = c
7Can 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
8Tools 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+
20The 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!
21Shakes 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)
303D 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…