@article{ISI:000089830500042,
 abstract = {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 antiferromagetically 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 gives an accurate value for the ground-state
energy only if the ratio J(2)/J(1) is less than about 0.2 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 low-energy (possibly gapless) states which
lie close to the ground state. We have also studied the spin-3/2 case
and find the low-energy effective Hamiltonians (LEH's) to be less
accurate there than in the spin-1/2 case. Finally, we have studied
nonlinear topologies where the LEH results deviate further from the
exact results.},
 author = {Raghu, C and Rudra, I and Ramasesha, S and Sen, D},
 doi = {10.1103/PhysRevB.62.9484},
 eissn = {2469-9969},
 issn = {2469-9950},
 journal = {PHYSICAL REVIEW B},
 month = {OCT 1},
 number = {14},
 pages = {9484-9492},
 times-cited = {19},
 title = {Evaluation of low-energy effective Hamiltonian techniques for coupled
spin triangles},
 unique-id = {ISI:000089830500042},
 volume = {62},
 year = {2000}
}