Imprints of Electron Angular Momentum on Molecular High-Harmonic Ellipticity in Linearly Polarized Laser Fields

We investigate the imprints of the initial electron angular momentum (EAM) on high-harmonic ellipticity generated from $\rm H_3^{2+}$ molecules in linearly polarized laser fields by solving the two-dimensional time-dependent Schrödinger equation (TDSE). Our results reveal that while both scalar orbital with zero EAM (A, $m=0$) and chiral orbital with nonzero EAM (E$^+$, $m=1$) exhibit periodic angular dependence of the HH ellipticity, their nodal structures display striking differences. Specifically, for the A orbital, the zero-ellipticity nodes are strictly locked to the geometric symmetry axes (e.g., $0^\circ$, $90^\circ$) of the $D_{3h}$ molecular frame. In contrast, for the E$^+$ orbital, the zero-ellipticity nodes exhibit an energy-dependent shift away from these axes, with the displacement evolving systematically across the harmonic spectrum. Through an analytical vector multi-center interference model, we demonstrate that this node shift originates from the symmetry breaking induced by the coupling between the orbital intrinsic phase winding associated with the initial electron angular momentum and the anisotropic Coulomb scattering phase of the returning electron. Furthermore, we show that these frequency-domain polarization signatures map directly onto the time domain, enabling the generation of polarization-tailored attosecond pulses. Our findings provide a comprehensive framework for decoding the interplay between geometric symmetry, orbital phase structure and ultrafast electron dynamics in strong-field processes.