Decay and renormalization in S=1 antiferromagnet Ba2FeSi2O7

The order parameter of S=1 easy-plane antiferromagnets can be characterized by a complex number. The phase fluctuations of the order parameter correspond to transverse modes (magnons), whereas amplitude fluctuations produce longitudinal modes. Due to the gapless nature of the transverse mode, the longitudinal mode is kinematically allowed to decay into pairs of transverse modes. Inelastic neutron scattering measurements on an effective S=1 tetragonal lattice compound Ba₂FeSi₂O₇reveal this decay and the consequent renormalization of the longitudinal and transverse mode dispersions. By applying a generalized linear spin wave theory with one-loop corrections, we reproduce the observed decay and the renormalization of the different modes. Moreover, by including corrections beyond one-loop, we obtain a very accurate estimate of the critical single-ion easy-plane anisotropy required to induce a quantum phase transition into a quantum paramagnetic state.

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Bulletin of the American Physical Society

APS March Meeting 2021

Volume 66, Number 1

Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA

Session R39: Exotic Magnetic Orders and Excitations

Abstract: R39.00003 : Decay and renormalization in S=1 antiferromagnet Ba2FeSi2O7

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Abstract: R39.00003 : Decay and renormalization in S=1 antiferromagnet Ba₂FeSi₂O₇