Evaluation of low-energy effective Hamiltonian techniques for coupled spin triangles

Дата и время публикации : 2000-02-07T16:51:14Z

Авторы публикации и институты :
C. Raghu (Indian Institute of Science, Bangalore)
Indranil Rudra (Indian Institute of Science, Bangalore)
S. Ramasesha (Indian Institute of Science, Bangalore)
Diptiman Sen (Indian Institute of Science, Bangalore)

Ссылка на журнал-издание: Phys. Rev. B 62 (2000) 9484-9492
Коментарии к cтатье: Revtex, 11 pages, 11 eps figures
Первичная категория: cond-mat.str-el

Все категории : cond-mat.str-el

Краткий обзор статьи: Motivated by recent work on Heisenberg antiferromagnetic spin systems on various lattices made up of triangles, we examine the low-energy properties of a chain of antiferromagnetically coupled triangles of half-odd-integer spins. We derive the low-energy effective Hamiltonian to second order in the ratio of the coupling J_2 between triangles to the coupling J_1 within each triangle. The effective Hamiltonian contains four states for each triangle which are given by the products of spin-1/2 states with the states of a pseudospin-1/2. We compare the results obtained by exact diagonalization of the effective Hamiltonian with those obtained for the full Hamiltonian using exact diagonalization and the density-matrix renormalization group method. It is found that the effective Hamiltonian is accurate only for the ground state for rather low values of the ratio J_2 / J_1 and that too for the spin-1/2 case with linear topology. The chain of spin-1/2 triangles shows interesting properties like spontaneous dimerization and several singlet and triplet excited states lying close to the ground state.

Category: Physics