Computing Effective Hamiltonians of Doped and Frustrated Antiferromagnets By Contractor Ren.pdfVIP

Computing Effective Hamiltonians of Doped and Frustrated Antiferromagnets By Contractor Renormalization Assa Auerbach Physics Department, Technion, Haifa 32000, Israel A review of the Contractor Renormalization (CORE) method, as a systematic derivation of the 5 low energy effective hamiltonian, is given, with emphasis on its differences and advantages over 0 traditional perturbative (weak/strong links) real space RG. For the low energy physics of the 2D 0 Hubbard model, we derive the plaquette bosons (projected SO(5)) model which connects the mi- 2 croscopic model to phases and phenomenology of high-Tc cuprates. For the S = 1/2 Pyrochlore t and Kagom´e antiferromagnets, the effective hamiltonians predict spin-disordered, lattice symmetry c breaking, ground states with a large density of low energy singlets as found by exact diagonalization O of small clusters. 7 2 I. RELIEF FROM STRONG FRUSTRATION ] l Frequently, interesting models of condensed matter systems involve strong local frustration. For example: the e - Heisenberg antiferromagnet given by r t s H = J S S , (1) . i j t a ij m- where ij are nearest neighbor bonds on lattices depicted in Fig.I. The classical (infinite spin size) groundst