Simulating high Tc cuprates.ppt

Simulating High Tc Cuprates Collaborators Y. C. Chen, Tung Hai University, Taichung, Taiwan R. Eder, Forschungszentrum, Karlsruhe, Germany C. M. Ho, Tamkang University, Taipei, Taiwan C. Y. Mou, National Tsinghua University, Taiwan Naoto Nagaosa, University of Tokyo, Japan C. T. Shih, Tung Hai University, Taichung, Taiwan Students: Chung Ping Chou, National Tsinghua University, Taiwan Wei Cheng Lee, UT Austin Hsing Ming Huang, National Tsinghua University, Taiwan Introduction To start simulation, need Hamiltonians! minimal models: 2D Hubbard model – exact diagonalization (ED) for 18 sites with 2 holes (Becca et al, PRB 2000) finite temp. quantum Monte Carlo (QMC) , fermion sign problem ( Bulut, Adv. in Phys. 2002) dynamic mean field theory and density matrix renormalization group, .. 2D t-J type models – Introduction To start simulation, need Hamiltonians! minimal models: 2D Hubbard model – exact diagonalization (ED) for 18 sites with 2 holes (Becca et al, PRB 2000) finite temp. quantum Monte Carlo (QMC) , fermion sign problem ( Bulut, Adv. in Phys. 2002). dynamic mean field theory and density matrix renormalization group, .. 2D t-J type models – no finite temp. QMC – sign problem and strong constraint ED for 32 sites with 4 holes (Leung, PRB 2006) Important info from experiments 5 possible phases: AFMI, AFMM, d-wave SC, and AFM+d-SC, normal metal. e-doped system is different from hole-doped.. The resonating-valence-bond (RVB) variational wave function proposed by Anderson ( originally for s-wave and no t’, t’’), The simplest way to include AFM: RVB + AFM for the half-filled ground state (no t, t’ and t’’) The wave function for adding holes to the half-filled RVB+AFM ground state Controversies about pairing Summary Variational approach has provided a number of semi-quantitative successes in understanding high Tc cuprates : ground state phase diagram and excitaiytons, spectral weight, STM co