Quantum squeezing and coherence of magnons detected by spin transport

We predict the emergence of novel magnetic quasiparticles, mediated by magnetic dipolar interactions, even for a uniform ground states. These quasiparticles exhibit a spin ranging from zero to above 1 [1]. Of particular interest is our finding that the eigenmodes in an easy-axis antiferromagnet are spin-zero quasiparticles instead of the widely believed spin-1 magnons [2]. These unusual properties originate from a competition between quantum mechanical squeezing (increasing the spin) and hybridization (decreasing the spin).We show that spin-current noise measurement can reveal this fundamental quantum phenomenon [1] in full analogy to the effective charge known from shot noise measurements. Antiferromagnetic magnons are shown to exhibit giant antanglement, which might be used as quantum battery [3]. Finally, we show that by adding two normal metal spin current detectors, the magnon coherence can be tested by measuring the cross correlations [4]in analogy to the well-kown second-order coherence.
[1] A. Kamra and W. Belzig, PRL 116, 146601 (2016).
[2] A. Kamra and W. Belzig, PRL 119, 197201 (2017).
[3] A. Kamra, E. Thingstad, G. Rastelli, R. A. Duine, A. Brataas, W. Belzig, and A. Sudbø, arXiv:1904.04553
[4] S. A. Bender, A. Kamra, W. Belzig, and R. A. Duine, PRL 122, 187701 (2019).