Title

Excitations and quantum fluctuations in site-diluted two-dimensional antiferromagnets

Authors

Authors

E. R. Mucciolo; A. H. Castro Neto;C. Chamon

Comments

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Abbreviated Journal Title

Phys. Rev. B

Keywords

LATTICE HEISENBERG-ANTIFERROMAGNET; SQUARE-LATTICE; MONTE-CARLO; 2; DIMENSIONS; FRACTONS; SIMULATIONS; SCATTERING; EXPANSION; BEHAVIOR; MAGNONS; Physics, Condensed Matter

Abstract

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.

Journal Title

Physical Review B

Volume

69

Issue/Number

21

Publication Date

1-1-2004

Document Type

Article

Language

English

First Page

15

WOS Identifier

WOS:000222530200073

ISSN

1098-0121

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