Heliciton-Assisted Chirality-Induced Spin Selectivity from Helical Dirac Current
Ju Gao, Fang Shen
• arXiv (quant-ph)
This paper formulates a microscopic quantum mechanism for Chirality-Induced Spin Selectivity (CISS) by introducing the "heliciton" a quantized, screw-symmetric environmental excitation. Through heliciton absorption and emission, local helical Dirac currents undergo inelastic resonant scattering that separates spin states into distinct momentum sidebands. The resulting spin polarization exhibits enantiomer-reversing symmetry and thermal occupation weighting without needing external magnetic fields or explicit spin-orbit coupling.
Heliciton-Assisted Chirality-Induced Spin Selectivity from Helical Dirac Current
Authors: Ju Gao, Fang Shen
Journal: arXiv (quant-ph)
Published: July 2026
A Quantized Environmental Mechanism for CISS
Chirality-Induced Spin Selectivity (CISS) describes the high spin polarization observed when electrons traverse chiral structures, a phenomenon that occurs despite the fact that conventional intrinsic spin-orbit coupling appears too small to provide a microscopic explanation. This paper resolves the missing dynamical bridge in CISS theory by promoting environmental screw coordinates to a quantized excitation called a Heliciton.
Physical Mechanism & Quantum Formulation
The Heliciton Quantum: Characterized as a screw-symmetric mode carrying phase φ - qz, longitudinal momentum ℏq, and energy ℏΩq.
Inelastic Sideband Mapping: In the first Born approximation, heliciton absorption and emission transform static local chiral couplings into resonant inelastic scattering channels:
Absorption: Converts |ψ↑, k; nq⟩ → |ψ↓, k+q; nq - 1⟩ (producing a spin-down sideband at k+q).
Emission: Converts |ψ↓, k; nq⟩ → |ψ↑, k-q; nq + 1⟩ (producing a spin-up sideband at k-q).
Thermally Weighted Polarization:
The polarization ratio within the resolved inelastic sideband sector is calculated as where thermal occupation is controlled by the Boltzmann factor &mathcal;O(T) = exp[-ℏΩq / (kBT)].
Thermal Regimes & Enantiomeric Reversal
Low-Temperature Asymmetry: As T → 0, the absorption branch is exponentially suppressed (&mathcal;O(T) → 0), while spontaneous emission retains its weight, driving the sideband polarization Psb → +1. Liquid-nitrogen temperatures (77 K) are sufficient to provide strong sideband asymmetry for modes above ℏΩq ∼ 13.6 meV.
Enantiosensitive Reversal: Reversing the physical screw handedness interchanges the spin identities of the two sidebands while leaving spectral and thermal factors intact, yielding P̄sb(k,q;T) = -Psb(k,q;T) across all temperatures.
One-Line Takeaway: CISS is microscopic sideband polarization driven by local geometric coupling between Dirac currents and quantized environmental helicitons, operating effectively without magnetic fields or explicit spin-dependent potentials.