Electromagnetic radiation force on a PEMC cylinder in a lossy medium

The purpose of this work is to extend the theoretical framework of radiation forces on a perfect electromagnetic conductor (PEMC) cylinder from an idealized lossless medium to a realistic <i>lossy</i> dielectric environment. This approach addresses a critical gap, as loss is ubiquitous, and fundamentally alters the transfer of electromagnetic momentum to particles. Employing the multipole expansion method adapted for complex permittivity, the longitudinal force assuming plane progressive waves with either TM or TE polarizations is derived from the Maxwell stress tensor based on a near-field scattering approach, and rigorously decomposed into its co-polarized and cross-polarized components. We demonstrate that the cross-polarized force component, which can be positive (pushing) or negative (pulling), exhibits a null-force condition. Most critically, the size parameter <i>k</i><i>a</i> at which this null occurs is not fixed, but is actively tunable by the loss of the medium (described by <i>ε</i>ext<i>'</i><i>'</i>). This tunability reveals a striking asymmetric polarization response: the null-point shift is monotonically decreasing for TM polarization but non-monotonic for TE polarization as absorption increases. Furthermore, we rigorously prove that the admittance-independence (denoted usually by the parameter <i>M</i>) of this null line, established in lossless media, is preserved. Moreover, numerical computations extended to a <i>lossy</i> water-like host medium (<i>ℜ</i>(<i>ε</i>_ext)=1.77) confirm that the non-monotonic force behavior is preserved in environments with a higher refractive index. The significance of this work relies on extending PEMC opto-mechanics to lossy media and revealing loss-tunable force nulls with possible sensing applications.