Dresden 2020 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 6: Cooperative Phenomena and Phase Transitions (joint session MA/TT)
TT 6.15: Talk
Monday, March 16, 2020, 13:00–13:15, HSZ 401
Orthomagnons and Quantum Weak Ferromagnetism in Kagome Antiferromagnets — •Robin R. Neumann1, Alexander Mook2, Jürgen Henk1, and Ingrid Mertig1,3 — 1Institut für Physik, Martin-Luther-Universität, D-06120 Halle — 2Department of Physics, University of Basel, CH-4056 Basel — 3Max-Planck-Institut für Mikrostrukturphysik, D-06120 Halle
Magnons are charge-neutral spin carriers that appear as excitations in magnetically ordered systems. The magnetic moment they carry is often thought to be antiparallel to the localized magnetic moments in the ground state, causing magnons in collinear (or coplanar) magnets to carry only those magnetic moment components offered by the texture.
In this talk, we lift the aforementioned limitation by introducing “orthomagnons,” whose magnetic moment has a component orthogonal to the magnetic texture. We demonstrate that the notion of orthomagnons appears naturally in coplanar antiferromagnets on the kagome lattice. As a consequence, both quantum and thermal fluctuations introduce a weak out-of-plane magnetic moment. In the limit of zero temperature, this gives rise to quantum weak ferromagnetism.