Magnons are the elementary excitations of spin systems. Here, we discuss the emergence of novel quasiparticles, mediated by magnetic dipolar interactions or anisotropies, that have been hiding in simple spin systems with uniformly ordered ground states. These quasiparticles exhibit a spin ranging from zero to above 1ℏ and display a variety of interesting quantum properties [1,2]. The unusual properties originate from quantum mechanical squeezing of the magnon vacuum state and its excitations. In antiferromagnets, the magnons are in highly entangled two-mode-squeezed states that might be a resource for quantum information [4]. We suggest that the quantum properties can be detected by noise correlations of spin transport across a magnet/non-magnetic conductor interface [3]. Finally, I touch on our recent attempts to uncover the quantum nature of squeezed magnons in optically induced non-linear magnonics [5]
Reference List
[1] A. Kamra and W. Belzig, Super-Poissonian shot noise of squeezed-magnon mediated spin transport, Phys. Rev. Lett. 116, 146601 (2016).
[2] A. Kamra, U. Agrawal, and W. Belzig, Noninteger-spin magnonic excitations in untextured magnets, Phys. Rev. B 96, 020411(R) (2017).
[3] A. Kamra and W. Belzig, Spin pumping and shot noise in ferrimagnets: bridging ferro- and antiferromagnets, Phys. Rev. Lett. 119, 197201 (2017).
[4] A. Kamra, E. Thingstad, G. Rastelli, R. A. Duine, A. Brataas, W. Belzig, and A. Sudbø, Antiferromagnetic Magnons as Highly Squeezed Fock States underlying Quantum Correlations, Phys. Rev. B 100, 174407 (2019)
[5] Ch. Schoenfeld, L. Feuerer, D. Wuhrer, W. Belzig, A. Leitenstorfer, D. Juraschek and D. Bossini, Dynamical renormalisation of a spin Hamiltonian via high-order nonlinear magnonics [arXiv:2310.19667]
