Gauge Field Induced Unconventional Skin Effect in Spinful Non-Hermitian Systems

The non-Hermitian skin effect (NHSE), a hallmark of non-Hermitian systems, stems from the topological nature of complex energy spectra, typically characterized by a non-zero spectral winding number. Beyond the spinless frameworks considered so far, here we realize a generic, tunable spinful NHSE in a 1D tight-binding lattice endowed with spin-dependent Abelian gauge fields. With proper tuning of the gauge parameter, we uncover an emergence of bidirected, spin-polarized zero-winding skin states, appearing in the absence of transpose-type time-reversal symmetry (T RS{\dag}) and featuring scale-restricted localization with non-Bloch spectral stability. While clearly distinct from the known Z2 and Critical NHSEs, these unconventional skin states evolve into them upon enforcing TRS{\dag} and introducing inter-spin coupling via magnetic fields, respectively. The magnetic field further drives a transition from a bidirectional to a unidirectional skin configuration. Our work unifies the previously known zero-winding NHSEs within a broader framework and provides experimentally accessible routes for realization in photonic and ultracold atomic systems with synthetic gauge fields.