Employing the concept of two-mode squeezed states from quantum optics, we demonstrate a revealing physical picture for the antiferromagnetic ground state and excitations. Superimposed on a Néel ordered configuration, a spin-flip restricted to one of the sublattices is called a sublatticemagnon. We show that an antiferromagnetic spin-up magnon is comprised by a quantum superposition of states with n+1 spin-up and n spin-down sublattice-magnons, and is thus an enormous excitation despite its unit net spin. Consequently, its large sublattice-spin can amplify its coupling to other excitations. Employing von Neumann entropy as a measure, we show that the antiferromagnetic eigenmodes manifest a high degree of entanglement between the two sublattices, thereby establishing antiferromagnets as reservoirs for strong quantum correlations. Based on these insights, we outline strategies for exploiting the strong quantum character of antiferromagetic (squeezed-)magnons and give an intuitive explanation for recent experimental and theoretical findings in antiferromagnetic magnon spintronics. arXiv:1904.04553v3 [cond-mat.mes-hall]

The plethora of recent discoveries in the field of topological electronic insulators has inspired a search for boson systems with similar properties. There are predictions that ferromagnets on a twodimensional honeycomb lattice may host chiral edge magnons. In such systems, we theoretically study how magnons and phonons couple. We find topological magnon-polarons around the avoided crossings between phonons and topological magnons. Exploiting this feature along with our finding of Rayleigh-like edge phonons in armchair ribbons, we demonstrate the existence of chiral edge modes with a phononic character. We predict that these modes mediate a chirality in the coherent phonon response and suggest measuring this effect via elastic transducers. These findings reveal a possible approach towards heat management in future devices.The first term describes the ferromagnetic exchange coupling between nearest neighbour sites, while the sec-arXiv:1808.05493v2 [cond-mat.mes-hall]

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