SKM 2023 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 33: Frustrated Magnets I

MA 33.6: Vortrag

Mittwoch, 29. März 2023, 16:30–16:45, HSZ 403

ZnCr₂Se₄ as a spiral-spin-liquid approximant — •D. S. Inosov¹, Y. V. Tymoshenko¹, A. Akopyan², D. Shukla², N. Prasai², M. Doerr¹, D. Gorbunov³, S. Zherlitsyn³, D. J. Voneshen^4,5, M. Boehm⁶, V. Tsurkan^7,8, V. Felea⁸, A. Loidl⁷, Y. O. Onykiienko¹, J. Ollivier⁶, and J. L. Cohn² — ¹IFMP, TU Dresden — ²University of Miami, Florida, USA — ³Hochfeld-Magnetlabor Dresden-Rossendorf — ⁴ISIS Facility, RAL, Didcot, UK — ⁵Royal Holloway University of London, UK — ⁶Institut Laue-Langevin, Grenoble, France — ⁷Institute of Physics, University of Augsburg — ⁸Institute of Applied Physics, Chisinau, Moldova

We investigated the cubic spinel helimagnet ZnCr₂Se₄ in its single-domain spin-spiral state by a combination of neutron scattering, thermal conductivity, ultrasound velocity, and dilatometry measurements. In zero magnetic field, the magnon spectrum consists of conventional gapless Goldstone modes and soft pseudo-Goldstone modes with a small energy gap of ∼0.17 meV. In an applied magnetic field, this gap closes nonmonotonically, so that upon reaching a critical field of 6 T, the gap vanishes over a whole 2D manifold in the reciprocal space. This was recently identified as a prerequisite for a putative spiral-spin-liquid ground state [see S. Gao et al., Phys. Rev. Lett. 129, 237202]. This highly unusual behavior of the spin gap causes large anomalies in thermal conductivity at subkelvin temperatures — nearly two orders of magnitude below the Néel temperature. Our results apply to a broad class of centrosymmetric Heisenberg helimagnets where discrete lattice symmetry is spontaneously broken by the magnetic order.