Quantum Monte Carlo (MC) simulations of the 2D S=1/2 Heisenberg antiferromagnet (AFM) with a vacancy and an applied magnetic field [1] showed that the characteristic decay length of the alternating magnetization around the defect displays an unexpected maximum in the neighborhood of the Berezinskii-Kosterlitz-Thouless (BKT) transition temperature. Given the role played in the BKT transition by vortex excitations, we investigated their contribution to the alternating-order behaviour, showing that isolated vortices modulate the parameters entering the effective model introduced in [1]: the temperature dependence of the vortex population allows us to explain the observed behaviour of the alternating-order decay length. We support such conclusions with MC simulations of the classical AFM, which also reveal some differences between the quantum and the classical model.

Vortex contribution to the defect-induced alternating magnetization in 2D antiferromagnets

Ruggero Vaia
2010

Abstract

Quantum Monte Carlo (MC) simulations of the 2D S=1/2 Heisenberg antiferromagnet (AFM) with a vacancy and an applied magnetic field [1] showed that the characteristic decay length of the alternating magnetization around the defect displays an unexpected maximum in the neighborhood of the Berezinskii-Kosterlitz-Thouless (BKT) transition temperature. Given the role played in the BKT transition by vortex excitations, we investigated their contribution to the alternating-order behaviour, showing that isolated vortices modulate the parameters entering the effective model introduced in [1]: the temperature dependence of the vortex population allows us to explain the observed behaviour of the alternating-order decay length. We support such conclusions with MC simulations of the classical AFM, which also reveal some differences between the quantum and the classical model.
2010
Istituto dei Sistemi Complessi - ISC
2D Heisenberg antiferromagnet
Magnetic impurity
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.14243/432781
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