Modulational Instability of Spinor Condensates in an Optical Lattice* *Supported by the National Natural Science Foundation of China under Grant No. 11274095 and the Program of USTITSPHP under Grant No. 13IRTSTHN016

Abstract

We obtain analytically the static states and corresponding collective-excitation spectra of a quasi-one-dimensional spin-1 condensate modulated by a long-wavelength optical lattice in the weak lattice limit. It is demonstrated that both ferromagnetic and antiferromagnetic condensates may exhibit dynamical instability, which agree with the results with numerical simulation. In the homogeneous limit, our results reduce to the previous results for homogeneous spinor condensates, i.e., dynamical instability can occur only for ferromagnetic interaction and an antiferromagnetic condensate is always dynamically stable.