Physics – Condensed Matter – Strongly Correlated Electrons
Scientific paper
2004-02-03
Phys. Rev. B 69, 214424 (2004)
Physics
Condensed Matter
Strongly Correlated Electrons
RevTex 4, 16 pages, 8 EPS figures, typos corrected, data from Ref. 9 added, few minor changes in the text, to appear in Phys.
Scientific paper
10.1103/PhysRevB.69.214424
We study the effect of site dilution and quantum fluctuations in an antiferromagnetic spin system on a square lattice within the linear spin-wave approximation. By performing numerical diagonalization in real space and finite-size scaling, we characterize the nature of the low-energy spin excitations for different dilution fractions up to the classical percolation threshold. We find nontrivial signatures of fractonlike excitations at high frequencies. Our simulations also confirm the existence of an upper bound for the amount of quantum fluctuations in the ground state of the system, leading to the persistence of long-range order up to the percolation threshold. This result is in agreement with recent neutron-scattering experimental data and quantum Monte Carlo numerical calculations. We also show that the absence of a quantum critical point below the classical percolation threshold holds for a large class of systems whose Hamiltonians can be mapped onto a system of coupled noninteracting massless bosons.
Castro Neto Antonio H.
Chamon Claudio
Mucciolo Eduardo R.
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