TY  - JOUR
A1  - Tymoshenko, Y. V.
A1  - Onykiienko, Y. A.
A1  - Müller, T.
A1  - Thomale, R.
A1  - Rachel, S.
A1  - Cameron, A. S.
A1  - Portnichenko, P. Y.
A1  - Efremov, D. V.
A1  - Tsurkan, V.
A1  - Abernathy, D. L.
A1  - Ollivier, J.
A1  - Schneidewind, A.
A1  - Piovano, A.
A1  - Felea, V.
A1  - Loidl, A.
A1  - Inosov, D. S.
T1  - Pseudo-Goldstone magnons in the frustrated \(S=3/2\) Heisenberg helimagnet \(ZnCr_2Se_4\) with a pyrochlore magnetic sublattice
JF  - Physical Review X
N2  - Low-energy spin excitations in any long-range ordered magnetic system in the absence of magnetocrystalline anisotropy are gapless Goldstone modes emanating from the ordering wave vectors. In helimagnets, these modes hybridize into the so-called helimagnon excitations. Here we employ neutron spectroscopy supported by theoretical calculations to investigate the magnetic excitation spectrum of the isotropic Heisenberg helimagnet \({ZnCr_2Se_4}\) with a cubic spinel structure, in which spin\(-3/2\) magnetic \({Cr^{3+}}\) ions are arranged in a geometrically frustrated pyrochlore sublattice. Apart from the conventional Goldstone mode emanating from the \((0~ 0~ {q_h})\) ordering vector, low-energy magnetic excitations in the single-domain proper-screw spiral phase show soft helimagnon modes with a small energy gap of \({∼0.17~ meV}\), emerging from two orthogonal wave vectors \(({q_h}~ 0~ 0)\) and \({(0~ {q_h}~ 0)}\) where no magnetic Bragg peaks are present. We term them pseudo-Goldstone magnons, as they appear gapless within linear spinwave theory and only acquire a finite gap due to higher-order quantum-fluctuation corrections. Our results are likely universal for a broad class of symmetric helimagnets, opening up a new way of studying weak magnon-magnon interactions with accessible spectroscopic methods.
KW  - physics
KW  - spin waves
KW  - helimagnets
KW  - inelastic neutron scattering
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-172770
VL  - 7
IS  - 4
ER  -