Equilibrium Spin Polarization Arising From Chirality

TL;DR

This paper introduces a quantum framework explaining how chiral molecules produce spin polarization at equilibrium, resolving previous paradoxes and predicting new magnetic ordering phenomena linked to chirality.

Contribution

It formulates a pseudo-Hermitian quantum model that accounts for equilibrium CISS, incorporating chirality through a non-local metric and deriving generalized Onsager relations.

Findings

Predicts chirality-induced spin magnetic ordering.

Reconciles equilibrium spin polarization with detailed balance.

Establishes a theoretical foundation for equilibrium CISS.

Abstract

Chirality-induced spin selectivity (CISS) describes how chiral molecules and materials generate spin polarization even at thermal equilibrium. This observation has challenged established principles of microscopic reversibility and Onsager reciprocity. We resolve this paradox by formulating a pseudo-Hermitian quantum framework in which structural chirality and electron correlations are sufficient to produce CISS observables. Chirality enters through a non-local metric that couples spin and spatial motion, leading to real spectra, unitary evolution, and thermodynamic consistency. The framework predicts a chirality-induced spin magnetic ordering characterized by a spin--displacement order $\langle \sigma \cdot x \rangle$, which reconciles equilibrium spin polarization with detailed balance and explains the persistence of CISS in materials composed of light elements. We also derive generalized Onsager-Casimir relations that respect the observed parity ($\mathcal{P}$) and time-reversal ($\mathcal{T}$) breaking, while preserving combined $\mathcal{PT}$-symmetry. This approach establishes a coherent foundation for equilibrium CISS and provides a route to link chemical chirality with measurable spin-to-charge conversion effects.