Dynamical structure factor of quasi-two-dimensional antiferromagnet in high fields

Abstract

We study high-field magnon dynamics and examine the dynamical structure factor in the quasi-2D tetragonal Heisenberg antiferromagnet with interlayer coupling corresponding to realistic materials. Within spin-wave theory, we show that a non-zero interlayer coupling mitigates singular corrections to the excitation spectrum occurring in the high-field regime that would otherwise require a selfconsistent approach beyond the 1/S approximation. For the fields between the threshold for decays and saturation field we observe widening of the two-magnon sidebands with significant shifting of the spectral weight away from the quasiparticle peak. We find spectrum broadening throughout large regions of the Brillouin zone, dramatic redistributions of spectral weight to the two-magnon continuum, two-peak structures and other features clearly unlike conventional single-particle peaks.

Field induced spontaneous quasiparticle decay and renormalization of quasiparticle dispersion in a quantum antiferromagnet

“…5c , the two-peak structures, distinct from the one-magnon state, appear in the spectrum and are accompanied by a suppression of the magnon intensity. These complex features are consistent with the theoretical prediction for spontaneous magnon decay and spectral weight redistribution from the quasiparticle peak to the two-magnon continuum at high fields 13 18 .…”

“…Although the key three-magnon coupling term is forbidden for the collinear ground state, it is present in an applied magnetic field when spins are canted along the field direction, i.e., the coupling is facilitated via a field-induced spin noncollinearity. To date, spontaneous magnon decay in canted AFMs has been thoroughly studied theoretically [12][13][14][15][16][17][18], but there have been very few detailed experimental studies due to the lack of materials with suitable energy scales. The only experimental evidence was reported by Masuda et al in an S =5/2 square-lattice AFM Ba 2 MnGe 2 O 7 [19], where the INS spectra become broadened in a rather narrow part of the Brillouin zone (BZ).…”

Quantum walk versus classical wave: Distinguishing ground states of quantum magnets by spacetime dynamics

“…where we recognize the typical form of the Bogolyubov factors [33]. Thus, we observe that the magnon density profile discussed in this paper is closely related to the usual form of the spin dynamical structure: The absolute values of the transversal components of S αβ (r, t ) provide information qualitatively similar to the magnon density profiles.…”

Dynamical and static spin structure factors of Heisenberg antiferromagnet on honeycomb lattice in the presence of Dzyaloshinskii-Moriya interaction

“…Also the normalized magnetic field value reported in the theoretical works is in the region 0 < gµ B B/J < 5.0. Also dynamical structure factor of two dimensional antiferromagnet in high fields has been investigated within spin-wave theory using self-consistent approach beyond the 1/S approximation 32 . The emergence of sharp peak in the frequency behavior of spin structure factor has been predicted in this work in analogy to our work.…”