Squeezing of nonlinear magnons in obliquely-magnetized nanowires under microwave pumping

摘要

Theoretical studies are reported for the non-classical quantum statistical behavior of bosonic excitations in obliquely-magnetized nanowires under condition of microwave pumping. A dipole-exchange Hamiltonian is employed in which the external magnetic field is transverse to the length of the ferromagnetic nanowire, causing the magnetization to be canted away from the symmetry axis. Using a coherent magnon states representation we obtain explicit results for the temporal evolution of the magnon creation and annihilation operators. Applications are presented in the perpendicular pumping configuration for the initial collapse and then revival of the magnon occupation number, the super-Poissonian magnon-counting statistics, and the magnon squeezing. It is found that all of these processes are enhanced by having an oblique-magnetization state in the nanowire. For comparison, we also present results when the microwave pumping field is in the orientation parallel to the magnetization. It is found that the parallel and perpendicular microwave pumping configurations lead to important differences in the time dependences.