Spin-Programmable Chiral Nanosolenoid

Updated 24 October 2025

Spin-programmable chiral nanosolenoids are nanoscale systems that use helical architecture to enforce robust, bias-tunable spin selectivity without static magnetic fields.
They integrate chirality with spin–orbit and momentum-dependent effects to achieve dynamic control over electron spin channels and magnetic flux generation.
Versatile realizations—from molecular wires to rolled magnetic layers—open pathways for innovations in spintronics, magnonics, and quantum information processing.

A spin-programmable chiral nanosolenoid is a nanoscale system in which electron or spin transport, magnetic or optical response, or local electromagnetic fields are determined by the interplay of geometric chirality and internal spin degrees of freedom. Typically realized by helically structured conductors, molecular wires, rolled-up magnetic layers, or engineered chiral potentials, these systems enable robust, bias-tunable, or even dynamically controllable spin selectivity, phase manipulation, and local magnetic field generation, often without the necessity of spin–orbit coupling or a static magnetic field. The essential functionalities emerge from the locking of spin and transport channels due to geometric asymmetry, symmetry-protected states, or the controlled conversion between chiral angular momentum (pseudo-angular momentum, chirality of phonons/modes) and actual spin polarization, with broad applications in spintronics, magnonics, quantum information, and nanoscale sensing.

1. Fundamental Mechanisms of Spin Selectivity in Chiral Nanosolenoids

Chiral-induced spin selectivity (CISS) is the foundational principle for spin-programmable chiral nanosolenoids. In helical systems—whether molecular (e.g., DNA, helical peptides), supramolecular (polymers, origami-based monolayers), or inorganic nanostructures (rolled nanowires, double or single-stranded magnetic helices)—strong coupling between electronic orbital motion and spin arises due to both broken inversion symmetry and the presence (or engineering) of internal electric fields or inter-atomic interactions (Medina et al., 2015, Sarkar et al., 2019, Wang et al., 2023, Wang et al., 2023, Wang et al., 2023).

In molecular helices, the transmission of electrons along well-oriented stacks of $p_z$ orbitals forms a "staircase" with fixed handedness, breaking inversion symmetry and, in conjunction with spin–orbit coupling (SOC), enables a $\pi_z$ – $\pi_z$ coupling through intermediate $p_{x,y}$ hopping. The effective Hamiltonian in cylindrical coordinates takes the generic form:

$H = \frac{1}{2m^*}(p_x^2 + p_y^2 + p_z^2) + \frac{\alpha}{\hbar}(p_x \sigma_y - p_y \sigma_x)$

where $\alpha$ encodes SOC strength. Upon projection onto the helical geometry, spin channels are split in energy, and under external bias one propagation/spin channel is preferentially occupied. The selection of spin is directly tied to the transport direction and chirality; varying the Fermi level, transport direction, or molecular handedness inverts spin preference (Medina et al., 2015).

Similar physics arises in magnetic helices (Sarkar et al., 2019) and chiral monolayers of twisted DNA origami (Wang et al., 2023), and also in inorganic rolled-up altermagnets, where the momentum-odd planar spin texture is welded onto a screw axis, locking the azimuthal current circulation with the spin channel in the absence of SOC (Chen et al., 22 Oct 2025).

2. Reciprocity and Functionalities: Direct, Inverse, and Programmable Modes

Chiral nanosolenoids exhibit reciprocal functionalities:

Direct mode: Injecting carriers with fixed spin polarization into a chiral helix or nanotube generates helical (axial–azimuthal) current whose handedness is determined by the spin. This produces an axial magnetic field $B_z$ with sign depending on spin orientation—a "spin-locked solenoid" effect (Chen et al., 22 Oct 2025).

For a nanotube of radius $R$ ,

$\tan \alpha_\sigma = \langle J_\theta^\sigma \rangle/\langle J_z^\sigma \rangle$

quantifies the current's chiral winding for spin $\sigma$ .

Inverse mode: A time-varying axial magnetic flux $\Phi(t)$ induces a circumferential electric field,

$E_\theta = -\frac{d\Phi}{dt}/(2\pi R)$

yielding equal and opposite axial currents for the two spin channels, which results in pure spin pumping:

$I_s = (\hbar/2e)(I_z^\uparrow - I_z^\downarrow)$

without net charge flow (Chen et al., 22 Oct 2025).

Spin programming: In chiral systems with discrete or continuous reconfigurability (e.g., electrically-switchable MEMS helices (Cong et al., 2018), origami-based DNA arrangements (Wang et al., 2023), or variable handedness in rolled nanotubes), spin selectivity and channel behavior can be tuned in situ. The chirality, Fermi level, applied bias, and presence of paramagnetic centers jointly enable dynamic or stateful spin programming, allowing tunable filtering or inversion of spin current and field direction.

3. The Role of Chirality, Spin–Orbit Coupling, and Symmetry

While strong SOC enhances spin selectivity, numerous results show that even in the absence of SOC, momentum-dependent spin filtering arises from geometry and symmetry:

In altermagnetic nanotubes, the rolling of a momentum-odd spin-polarized, net-zero magnetization 2D material into a cylinder induces axial–azimuthal coupling, with spin control arising purely from the locked symmetry, not from SOC (Chen et al., 22 Oct 2025).
In polyaniline helical nanofibers assembled from achiral monomers, supramolecular helicity alone can yield spin selectivity under both longitudinal and transverse electron injection, with effective SOC arising from chiral electron hopping (Wang et al., 2023).
In systems exhibiting chiral phonon activated spin currents (Li et al., 2021, Fransson, 2022), phonon angular momentum with definite handedness, transferred to electrons by vibronically assisted SOC, permits spin programming in the complete absence of static magnetic or SOC-based effects.

In all cases, spin selectivity can be enhanced, inverted, or even produced solely by the geometry-induced phase correlation imposed by the chiral path, as formalized by the presence of a quantized pseudo-angular momentum (PAM) label for Bloch electrons in screw-symmetric lattices or molecules (Wang et al., 2023).

4. Quantitative Models, Coherence, and Room-Temperature Operation

Transport models for chiral nanosolenoids incorporate:

Tight-binding and continuum Hamiltonians, including $p_z$ – $p_{x,y}$ orbital mixing, Rashba/Dresselhaus-like SOC, and explicit helical geometry (Medina et al., 2015, Diaz et al., 2017, Sarkar et al., 2019).
Nonlinear interactions in deformable molecular systems, yielding soliton solutions with enhanced spin projection:

$|\mathrm{SP_{sol}}| = \frac{1}{\sqrt{1+\gamma^2}}$

for bright soliton amplitude and spin polarization (Diaz et al., 2017).

In programmable chiral nanowires, engineered chiral potentials induce an effective spin–orbit field, resulting in oscillatory transmission as a function of field and gate-tuned chemical potential. The oscillations reveal coherent precession phenomena, mapping the interplay between geometric and spin degrees of freedom (Briggeman et al., 8 Feb 2025).
At experimental scales, phase coherence is limited; the transmission is then modeled as the product of sequential coherent segments of length $\ell_\phi$ , ensuring persistence of spin selectivity over device-relevant distances and robust performance at room temperature (Medina et al., 2015, Torres-Cavanillas et al., 2019).

5. Material Realizations and Device Architectures

Spin-programmable chiral nanosolenoids have been engineered in a diversity of material platforms:

Rolled-up altermagnetic nanotubes: V $_2$ Se $_2$ O calculated to harbor spin-dependent azimuthal winding of Bloch states, enabling SOC-free spin-programmable solenoid operation and pure spin pumping via time-varied flux (Chen et al., 22 Oct 2025).
DNA origami chiral monolayers: Twisted DNA origami structures arranged as perpendicular monolayers show up to an order-of-magnitude enhancement in spin-filtering efficiency per area compared to conventional dsDNA, with tertiary structure (overall twist) as a key parameter for Normalized Spin Polarization (NSP), e.g., NSP up to +48% for R-TDO architectures (Wang et al., 2023).
Chiral magnetic helices and artificial double helices: Patterned magnetic nanostructures, by 3D nano-patterning (e.g., FEBID), balance exchange and dipolar interactions to geometrically fix domain wall chirality and realize programmable chiral magnetic domain textures with topological defects (Sanz-Hernández et al., 2020).
MEMS-based programmable chiral photonic devices: Electrically actuated microhelices can switch between four chirality states (D, L, racemic, achiral), implementing logical operations and reconfigurable chiral photonic response; miniaturization suggests an analog at the nanoscale for spin-progammable solenoids (Cong et al., 2018).
Polyaniline helical fibers and metallopeptides: Achiral monomers self-assembled into chiral nanofibers or peptides with paramagnetic cores display large, even bias-tunable, room-temperature spin polarization, directly linking supramolecular structure to device-level CISS effect and programming options (Wang et al., 2023, Torres-Cavanillas et al., 2019).

6. Applications: Spintronics, Magnonics, and Quantum Information

Spin-programmable chiral nanosolenoids function as:

Programmable spin filters, spin injectors, pure spin current pumps, or spin–locked magnetic flux generators, extending to low-energy, charge-neutral operations (Chen et al., 22 Oct 2025).
Stereoselective sensors and opto-spin devices, exploiting the logic-level reconfigurability or dynamic chirality of nanoscale architectures (Cong et al., 2018, Karakhanyan et al., 2023).
Key elements in magnonic logic, with chiral magnon resonators or programmable phase inverters operating as logic and memory elements, and in neural/memcomputing architectures (Kruglyak, 2021, Baumgaertl et al., 2021).
Topological transport channels for nontrivial spin textures, including skyrmions and chiral spin-spirals, with electrical readout via chiral planar or anomalous Hall effects (Kipp et al., 2021).
Quantum simulation platforms where engineered chirality, SOC, and pairing can support analog models of quantum phases and function as testbeds for fundamental questions of spin-momentum entanglement in condensed matter (Briggeman et al., 8 Feb 2025).

7. Perspectives and Future Directions

Further research is focusing on:

Implementing full dynamic control over chirality and spin selection by electrical, mechanical, optical, or thermally driven means (e.g., via chirality-tunable materials, external gating, controllable assembly).
Exploring nonrelativistic spintronic architectures that eliminate heavy elements or external fields, capitalizing on crystal symmetry and geometry for robust and energy-efficient spin control (Chen et al., 22 Oct 2025).
Scaling to complex circuits with spatial or spectral multiplexing, integrating chiral nanosolenoids with established semiconductor, biological, or magnonic platforms for advanced information processing and sensing.
Expanding the fundamental theoretical framework, notably the role of pseudo-angular momentum in chiral lattices (Wang et al., 2023), the quantification of topological and chiral responses (gradient expansions, Berry-phase mechanisms (Kipp et al., 2021)), and the interface physics for maximizing conversion between chiral momentum and true spin polarization.
Optimizing coherence and transport in programmable chiral devices for high-fidelity, low-dissipation, room-temperature operation, bridging the gap to practical quantum and spintronic implementations.

In summary, the spin-programmable chiral nanosolenoid encapsulates a rich interplay between geometry, symmetry, and spin, with demonstrated functionalities including directional spin filtering, logic operations, pure spin current generation, and programmable magnetic field control. Its realizations span organic, inorganic, photonic, and magnetic systems, providing a fertile ground for both fundamental research and technology development in chiral spintronics and nanoscale quantum devices (Medina et al., 2015, Sarkar et al., 2019, Wang et al., 2023, Wang et al., 2023, Wang et al., 2023, Karakhanyan et al., 2023, Briggeman et al., 8 Feb 2025, Chen et al., 22 Oct 2025).