Non-Hermitian physics of levitated nanoparticle array

The nonreciprocal interaction between two levitated nanoparticles is induced by the phase difference between the trapping lasers [1]. Such a system is naturally interpreted as a non-Hermitian system which effectively describes a nonequilibrium system. In this work, we propose that a levitated nanoparticle array is an ideal platform to investigate non-Hermitian physics. Then, the non-Bloch band theory [2] can analyze the behavior of the system. We find appearance of the dynamical-instability phase induced by the nonreciprocal hopping amplitude. Furthermore, we reveal that the continuum band has a branch point associated with the singularity point of the generalized Brillouin zone. [1] J. Rieser et al., Science 377, 987 (2022). [2] K. Yokomizo et al., Phys. Rev. Lett. 123, 066404 (2019).