Chirality-Induced Orbital-Angular-Momentum Selectivity

• CIOAMS is a chirality-driven effect where broken symmetry produces selective orbital angular momentum textures in materials such as topological insulators and chiral nanostructures.
• It manifests in various platforms, including ARPES studies of Bi2Se3 surface states, plasmon-enhanced molecular optics, and orbital Edelstein responses in chiral conductors.
• Its theoretical framework relies on broken inversion and mirror symmetries, leading to chirality-dependent dipole selection, orbital hybridization, and interference effects observable in dichroism and transport experiments.

Searching arXiv for papers on CIOAMS and related orbital selectivity mechanisms. Chirality-Induced Orbital-Angular-Momentum Selectivity (CIOAMS) designates a class of chirality-dependent phenomena in which orbital angular momentum (OAM) is selectively generated, transmitted, absorbed, or detected because handedness breaks left/right equivalence in the relevant electronic, optical, or vibronic states. In the literature, the term is used in several closely related but not identical senses: momentum-selective photoexcitation from chiral OAM textures in topological surface states, OAM-dependent molecular absorption in plasmonic near fields, chirality-dependent orbital Edelstein responses in chiral conductors, interatomic OAM textures in chiral crystals, and phonon-mediated orbital transfer in helical lattices (Park et al., 2011). A common thread is that structural or field-induced chirality produces an OAM texture or an OAM-sensitive matrix element whose sign reverses under enantiomer exchange, momentum inversion, or reversal of the OAM quantum number, depending on the platform.

1. Terminology, scope, and representative realizations

The most precise use of CIOAMS depends on platform. In Bi$_2$Se$_3$, the term refers to polarization- and momentum-selective excitation enabled by a chiral in-plane OAM texture of the Dirac surface states, detected by circular-dichroism ARPES and linked to spin- and OAM-polarized photocurrent generation (Park et al., 2011). In plasmon-enhanced molecular optics, CIOAMS denotes differential absorption of optical OAM by a chiral molecule placed in the near field of a nanoparticle or nanoparticle cluster, where plasmonic scattering lifts the otherwise vanishing free-space average interaction (Wu et al., 2017). In chiral conductors such as carbon nanotubes and Te-like helical crystals, the same phrase or its close variant is used for current-induced orbital polarization governed by the orbital Edelstein effect, itinerant OAM textures, or orbital filtering in transport (Göbel et al., 10 Apr 2025).

This multiplicity of usage is not merely terminological. It reflects distinct microscopic channels by which chirality can enter the OAM sector: through Bloch-state orbital hybridization, dipole-selection rules in photoemission, focused optical-vortex fields, helical electrostatic confinement, interatomic hopping phases, or chiral phonon vertices. A plausible implication is that CIOAMS functions less as a single mechanism than as an umbrella concept for chirality-driven OAM selectivity across condensed-matter, optical, and transport settings.

Platform	CIOAMS manifestation	Representative paper
Bi$_2$Se$_3$ surface states	chiral OAM texture and circular-dichroic photoexcitation	(Park et al., 2011)
Chiral molecule near plasmonic NP cluster	OAM-dependent absorption, OAM dichroism	(Wu et al., 2017)
CoSi and related chiral crystals	bulk OAM texture, monopole-like orbital-momentum locking, icCD	(Brinkman et al., 2024)
Chiral CNTs	orbital Edelstein susceptibility, orbital filtering	(Shmayev et al., 20 Jun 2026)
Chiral Te	spin-free interatomic OAM in isolated $5s$ bands	(Oh et al., 20 May 2026)
Chiral phonon / helical crystal systems	phonon-driven orbital transfer and finite-$q$ orbital selectivity	(Tateishi et al., 28 Apr 2026)

A recurrent misconception is to identify CIOAMS exclusively with optical OAM beams. That identification is too narrow. Several works treat CIOAMS as an intrinsic property of Bloch states in chiral solids or as a transport response with no incident optical vortex at all (Hagiwara et al., 2024).

2. Symmetry origin and minimal theoretical structures

Across realizations, CIOAMS requires broken inversion and, more stringently in many cases, broken mirror or improper symmetries. In B20 CoSi, the absence of inversion and all improper symmetries permits an imaginary hybridization of orbitals of opposite mirror parity, generating a finite bulk OAM texture even in the absence of magnetism or strong spin-orbit coupling. In the plane of incidence, the lowest two branches near $\Gamma$ can be represented as

$$|\psi_k\rangle \simeq c_1(k)|d_{xz}\rangle + i\,c_2(k)|d_{xy}\rangle,$$

with $c_2(-k)=-c_2(k)$, leading to $L_x(k_x)\propto \gamma(k_x)$, $_3$0, and enantiomer reversal $_3$1 (Brinkman et al., 2024).

For topological-insulator surface states, a minimal Hamiltonian that retains both spin-momentum locking and local OAM coupling is

$_3$2

where the Rashba-like term produces the helical spin texture and the $_3$3 term endows the Bloch states with chiral OAM locked to momentum (Park et al., 2011). In Bi$_3$4Se$_3$5, the OAM lies in-plane and perpendicular to $_3$6, with

$_3$7

and $_3$8 from DFT (Park et al., 2011).

In chiral topological semimetals, the orbital sector can itself furnish the low-energy topology. A minimal $_3$9 model around a threefold node is

$_2$0

with eigenstate expectation values

$_2$1

so that $_2$2 and the OAM texture acts as the primary origin of nonzero orbital Chern number even when spin-orbit coupling is negligible (Hagiwara et al., 2024).

One-dimensional helical systems admit a different microscopic route. In the discrete-helix three-orbital model, chirality alone generates odd-in-$_2$3 OAM textures through Slater-Koster hybridization in the local basis $_2$4, with $_2$5 identically while $_2$6 and $_2$7 remain finite (Cordova et al., 15 May 2026). In analytically solvable orbital-Edelstein models, even a three-site helix of $_2$8-orbitals repeated along $_2$9 produces a large inter-site orbital response because the complex hopping phases around the spiral encode the geometry directly into the orbital sector (Göbel et al., 7 Feb 2025).

3. Momentum-space textures and spectroscopic observables

Angle-resolved photoemission, especially with circular polarization, has provided the most direct momentum-resolved evidence for CIOAMS in solids. In Bi$_3$0Se$_3$1, circular dichroism is defined as

$_3$2

and was found to oscillate $_3$3 with an amplitude up to $_3$4. The sign reversal across the Dirac point indicates opposite OAM chirality in the upper and lower cones, and the relation $_3$5 identifies the dichroism with a tangential OAM texture perpendicular to $_3$6 (Park et al., 2011).

In CoSi, the analogous observable is the intrinsic chiral circular dichroism,

$_3$7

which isolates the chirality-driven contribution from the geometry-induced background. Soft-X-ray ARPES on opposite enantiomers showed $_3$8 and a dipolar $_3$9 distribution centered at $5s$0, consistent with monopole-like OAM locking in the bulk bands. The chiral dichroism reaches $5s$1–$5s$2 of the peak photoemission intensity (Brinkman et al., 2024).

Te extends this line of work by separating OAM from spin. In isolated $5s$3 bands, CD-ARPES with light incident in the $5s$4 plane and photoelectrons collected along the A-$5s$5-A direction resolved opposite dichroism on bands with opposite velocity, while spin-resolved ARPES found zero spin asymmetry in $5s$6. First-principles analysis distinguished $5s$7, which vanishes identically for the $5s$8 states, from $5s$9, which remains finite and matches the chiral-chain CIOAMS texture (Oh et al., 20 May 2026).

These results clarify a second common misconception: circular dichroism in photoemission is not automatically a spin texture proxy. In several of these materials, the dichroic signal is explicitly formulated as an OAM-sensitive quantity, and in Te the measured states are spin-free despite robust dichroism (Oh et al., 20 May 2026).

4. Optical-vortex, molecular, and mesoscopic manifestations

In optical matter-coupling problems, CIOAMS often denotes differential response to the sign of optical OAM. A key negative baseline is that in free space a chiral molecule exhibits no net difference in absorption between an OAM beam of topological charge $q$0 and one of charge $q$1 once averaged over all molecular positions and orientations. Plasmonic resonances alter this conclusion by creating highly inhomogeneous local fields and hot spots where the field intensity and local optical chirality density

$q$2

can be two to three orders of magnitude larger than in the incident beam (Wu et al., 2017).

Within the T-matrix treatment, the total fields at the molecule are $q$3 and $q$4, and the molecular absorption rate is

$q$5

The OAM dichroism is defined as

$q$6

For a gold sphere of radius $q$7 in water, a molecule $q$8 from the surface experiences a $q$9 enhancement of the OAM dichroism at $\Gamma$0, plus a new dichroic band around $\Gamma$1. For a gold dimer of two $\Gamma$2 spheres separated by $\Gamma$3, field enhancements exceed $\Gamma$4 at the coupled SPR $\Gamma$5, and plasmon-induced OAM dichroism near the molecular UV band is $\Gamma$6 larger than with a single sphere, exceeding $\Gamma$7 at the plasmon band (Wu et al., 2017).

A different optical route is the QED analysis of twisted-light absorption. There the discriminatory term is the $\Gamma$8 interference in single-photon absorption, yielding for fixed molecular orientation

$\Gamma$9

This mechanism requires the electric quadrupole and optical spin; in an isotropic fluid, the rotational average of $$|\psi_k\rangle \simeq c_1(k)|d_{xz}\rangle + i\,c_2(k)|d_{xy}\rangle,$$0 vanishes, so the CIOAMS signal vanishes. By contrast, partially ordered chiral films can retain the effect (Forbes et al., 2018).

At mesoscopic scales, direct OAM-geometry coupling has been observed in reflectance from fabricated helical microstructures. Helical dichroism is defined as

$$|\psi_k\rangle \simeq c_1(k)|d_{xz}\rangle + i\,c_2(k)|d_{xy}\rangle,$$1

or equivalently

$$|\psi_k\rangle \simeq c_1(k)|d_{xz}\rangle + i\,c_2(k)|d_{xy}\rangle,$$2

For a left-handed structure with $$|\psi_k\rangle \simeq c_1(k)|d_{xz}\rangle + i\,c_2(k)|d_{xy}\rangle,$$3 and $$|\psi_k\rangle \simeq c_1(k)|d_{xz}\rangle + i\,c_2(k)|d_{xy}\rangle,$$4, $$|\psi_k\rangle \simeq c_1(k)|d_{xz}\rangle + i\,c_2(k)|d_{xy}\rangle,$$5 peaks at $$|\psi_k\rangle \simeq c_1(k)|d_{xz}\rangle + i\,c_2(k)|d_{xy}\rangle,$$6 with $$|\psi_k\rangle \simeq c_1(k)|d_{xz}\rangle + i\,c_2(k)|d_{xy}\rangle,$$7, while the right-handed enantiomer gives $$|\psi_k\rangle \simeq c_1(k)|d_{xz}\rangle + i\,c_2(k)|d_{xy}\rangle,$$8 at the same $$|\psi_k\rangle \simeq c_1(k)|d_{xz}\rangle + i\,c_2(k)|d_{xy}\rangle,$$9; an achiral cylinder yields $c_2(-k)=-c_2(k)$0 for all $c_2(-k)=-c_2(k)$1. The reported maximum remains $c_2(-k)=-c_2(k)$2 across the tested diameters and pitches (Ni et al., 2018).

These optical realizations underline a third misconception: strong OAM-based chiral discrimination does not follow from OAM alone. The molecular and mesoscopic results both emphasize matching conditions—plasmonic near-field localization, orientational order, or scale matching between the vortex-ring diameter and the helical structure—rather than a universal free-space OAM-chirality coupling (Wu et al., 2017).

5. Nonequilibrium transport, orbital Edelstein physics, and orbital filtering

In transport settings, CIOAMS is closely connected to the orbital Edelstein effect, which converts a longitudinal bias into orbital magnetization. For chiral CNTs, the orbital Edelstein susceptibility is defined by

$c_2(-k)=-c_2(k)$3

or, in device form,

$c_2(-k)=-c_2(k)$4

In low-energy Dirac theory, chiral CNTs with broken inversion symmetry admit a term $c_2(-k)=-c_2(k)$5, with $c_2(-k)=-c_2(k)$6, and the resulting susceptibility is an odd function of chirality angle and proportional to radius. For metallic tubes close to the Fermi level,

$c_2(-k)=-c_2(k)$7

making the response tunable by doping or gate voltage (Göbel et al., 10 Apr 2025).

The broader nonequilibrium survey of CNTs shows that $c_2(-k)=-c_2(k)$8 does not obey a universal diameter-scaling law. Instead, metallic and semiconducting tubes split into family-dependent branches when plotted against $c_2(-k)=-c_2(k)$9. Metallic CNTs recover their intrinsic orbital response within $L_x(k_x)\propto \gamma(k_x)$0–$L_x(k_x)\propto \gamma(k_x)$1 unit cells ($L_x(k_x)\propto \gamma(k_x)$2–$L_x(k_x)\propto \gamma(k_x)$3) away from wide-band metallic contacts, whereas semiconducting tubes exhibit oscillatory $L_x(k_x)\propto \gamma(k_x)$4, $L_x(k_x)\propto \gamma(k_x)$5, and $L_x(k_x)\propto \gamma(k_x)$6 profiles arising from interference between channels with different crystal angular momenta. By injecting an azimuthally phased contact self-energy, one obtains perfect angular-momentum gaps such that only $L_x(k_x)\propto \gamma(k_x)$7 transmits at a given energy (Shmayev et al., 20 Jun 2026).

Tellurium-based models and first-principles density-matrix dynamics further connect current-driven orbital polarization to CISS-like responses. In trigonal Se, the local orbital polarization

$L_x(k_x)\propto \gamma(k_x)$8

is generated by transport along the chiral axis and shows a weak dependence on SOC, unlike the spin polarization $L_x(k_x)\propto \gamma(k_x)$9. In the coherent regime at $_3$00, the reported values are $_3$01 and $_3$02, while at the equilibrium structural chirality $_3$03 both rise monotonically with increasing chirality and reach $_3$04, $_3$05 as $_3$06 (Gupta et al., 5 Aug 2025).

Analytically solvable helix models sharpen the hierarchy between orbital and spin responses. In the three-site $_3$07-orbital helix, the maximal orbital susceptibility for Te parameters is reported as

$_3$08

while first-principles and Boltzmann estimates for the spin Edelstein effect give $_3$09, implying $_3$10 (Göbel et al., 7 Feb 2025). This suggests that in chiral conductors the orbital channel can be the dominant nonequilibrium angular-momentum reservoir even when spin selectivity is the experimentally monitored quantity.

Transport CIOAMS also appears in direct electron propagation through chiral potentials. In a helical electrostatic confinement with center winding on a helix of radius $_3$11 and pitch $_3$12, rotating-frame reduction yields

$_3$13

which couples linear and orbital motion (Cho et al., 9 Sep 2025). For an incoming OAM eigenstate $_3$14, the transmission amplitude through a chiral region depends on handedness through $_3$15, and realistic DNA-like parameters produce $_3$16 and orbital polarization up to $_3$17–$_3$18, increasing with the number of chiral turns and remaining robust against static disorder (Cho et al., 9 Sep 2025).

6. Relation to spin selectivity, phonons, and current directions of the field

A major contemporary theme is the relation between CIOAMS and CISS. Several studies explicitly propose orbital polarization as the microscopic precursor of spin polarization. In Bi$_3$19Se$_3$20, circularly polarized excitation selects momentum sectors through dipole rules $_3$21, with

$_3$22

so that a singly degenerate spin-polarized surface band converts OAM-selective optical excitation directly into a unidirectional spin-polarized photocurrent (Park et al., 2011). In CoSi, the bulk OAM monopole is proposed as a microscopic route for CISS through OAM-to-spin conversion at interfaces or via residual SOC (Brinkman et al., 2024).

The Se density-matrix treatment makes the distinction sharper. There, structural chirality first imprints a finite $_3$23 on Bloch states, and SOC-mixed wavefunctions render electron-phonon scattering spin dependent. The full Lindblad dynamics then yields a spatially growing $_3$24 and $_3$25, with a nonzero bulk offset in $_3$26. This behavior differs from the colinear Edelstein effect, which produces a uniform bulk spin polarization with no intrinsic orbital selectivity (Gupta et al., 5 Aug 2025).

Chiral phonons provide yet another route to CIOAMS. In a threefold helical crystal, the rotational electron-phonon interaction couples directly to $_3$27, enforcing the ladder rule

$_3$28

by crystal angular-momentum conservation. The induced $_3$29 is suppressed near $_3$30 and the zone boundary, and enhanced at intermediate wave vectors where chiral phonon branches split and the rotational content is maximal (Tateishi et al., 28 Apr 2026). Related vibronic work in NaYbSe$_3$31 shows angular-momentum transfer $_3$32 between a degenerate phonon doublet and an orbital excitation in a vibronic bound state, demonstrating that chiral phonons can become well-defined angular-momentum carriers through orbital coupling (Pai et al., 2022). In honeycomb and TMD models, adiabatic chiral phonon cycles dynamically induce electronic OAM through a Berry-phase mechanism, with the sign locked to phonon chirality (Yao et al., 12 Nov 2025).

Two broad research directions follow from these results. First, multiple platforms now support “spin-free” or weak-SOC orbital functionality, most explicitly the interatomic OAM states in chiral Te and the orbital-dominant responses in helical transport models (Oh et al., 20 May 2026). Second, a unifying orbitronics perspective is emerging in which chirality, not necessarily strong atomic SOC, is the minimal ingredient for generating useful orbital textures, orbital currents, and orbital filters (Cordova et al., 15 May 2026).

The main unresolved issue is not whether chirality can act on OAM, but which microscopic channel dominates in a given experiment. Depending on platform, the decisive ingredient may be $_3$33 locking, inter-site hopping geometry, plasmon-enhanced near fields, contact-induced channel interference, linear-orbital coupling, or chiral phonon transfer. This suggests that CIOAMS is best understood as a symmetry-governed family of orbital-selection phenomena rather than a single universal mechanism.