Excitation of nonlinear longitudinal structures in spin-1/2 quantum plasma in the presence of ion beam

The formation of longitudinal, nonlinear structures in an interacting ion beam, spin-1/2 quantum, electron-ion plasma is reported by employing a separate spin evolution quantum hydrodynamic model (SSE-QHD). The reductive perturbation method is followed to develop the KdV equations. In the presence of an ion beam and keeping the finite electron inertial effects, ion acoustic (IA) soliton and spin electron acoustic (SEA) soliton are found. The critical values of beam speed and spin polarization, required for the existence of solitary structures, are highlighted. It is prescribed that the present model supports rarefactive and compressive SEA soliton and compressive IA soliton. It is shown that the ion beam is essential for the existence of a compressive SEA solitary structure. We have also calculated and compared the energy densities of  both solitons. Furthermore, the dependence of the nonlinear structures on the beam parameters and spin polarization are also examined. Our findings would be useful to understand the new spin-dependent nonlinear structures as well as the features of nonlinear IA waves in ion beam–plasma interactions.