Authors
Yoshito Watanabe, Simon Trebst, Ciarán Hickey
Published in
Physical review letters. Volume 134. Issue 10. Pages 106703. Mar 14, 2025.
Abstract
Local moments with a spin S>1/2 can exhibit a rich variety of elementary quasiparticle excitations, such as quadrupolar excitations, that go beyond the dipolar magnons of conventional spin-1/2 systems. However, the experimental observation of such quadrupolar excitations is often challenging due to the dipolar selection rules of many linear response probes, rendering them invisible. Here we show that nonlinear spectroscopy, in the form of two-dimensional coherent spectroscopy (2DCS), can be used to reveal quadrupolar excitations. Considering a family of spin-1 Heisenberg ferromagnets with single-ion easy-axis anisotropy as an example, we explicitly calculate their 2DCS signature by combining exact diagonalization and generalized spin wave theory. We further demonstrate that 2DCS can provide access to the quadrupolar weight of an excitation, analogous to how linear response provides access to the dipolar weight. Our work highlights the potential of nonlinear spectroscopy as a powerful tool to diagnose multipolar excitations in quantum magnets.
PMID:
40153654
Bibliographic data and abstract were imported from PubMed on 29 Mar 2025.
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