TY  - JOUR
AU  - Tymoshenko, Y. V.
AU  - Onykiienko, Y. A.
AU  - Müller, T.
AU  - Thomale, R.
AU  - Rachel, S.
AU  - Cameron, A. S.
AU  - Portnichenko, P. Y.
AU  - Efremov, D. V.
AU  - Tsurkan, V.
AU  - Abernathy, D. L.
AU  - Ollivier, J.
AU  - Schneidewind, Astrid
AU  - Piovano, A.
AU  - Felea, V.
AU  - Loidl, A.
AU  - Inosov, D. S.
TI  - Pseudo-Goldstone Magnons in the Frustrated S=3=2 Heisenberg Helimagnet ZnCr2Se4with a Pyrochlore Magnetic Sublattice
JO  - Physical review / X
VL  - 7
SN  - 2160-3308
CY  - College Park, Md.
PB  - APS
M1  - FZJ-2017-07932
SP  - 041049
PY  - 2017
AB  - Low-energy spin excitations in any long-range ordered magnetic system in the absence of magnetocrystallineanisotropy are gapless Goldstone modes emanating from the ordering wave vectors. Inhelimagnets, these modes hybridize into the so-called helimagnon excitations. Here we employ neutronspectroscopy supported by theoretical calculations to investigate the magnetic excitation spectrum of theisotropic Heisenberg helimagnet ZnCr2Se4 with a cubic spinel structure, in which spin-3=2 magnetic Cr3þions are arranged in a geometrically frustrated pyrochlore sublattice. Apart from the conventionalGoldstone mode emanating from the ð0 0 qhÞ ordering vector, low-energy magnetic excitations in thesingle-domain proper-screw spiral phase show soft helimagnon modes with a small energy gap of∼0.17 meV, emerging from two orthogonal wave vectors ðqh 00Þ and ð0 qh 0Þ where no magnetic Braggpeaks are present. We term them pseudo-Goldstone magnons, as they appear gapless within linear spinwavetheory and only acquire a finite gap due to higher-order quantum-fluctuation corrections. Our resultsare likely universal for a broad class of symmetric helimagnets, opening up a new way of studying weakmagnon-magnon interactions with accessible spectroscopic methods.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000416432000002
DO  - DOI:10.1103/PhysRevX.7.041049
UR  - https://juser.fz-juelich.de/record/840399
ER  -