Helicity-Resolved Spatiotemporal Mapping of Chiral Plexcitons in Helicoids

Amitav Sahu; In Han Ha; Jaeyeon Jo; Jeong Hyun Han; Jiawei Lv; Ki Tae Nam; Miyoung Kim; Pavel Chabera; Ryeong Myeong Kim; Sankaran Ramesh

arxiv: 2606.09097 · v1 · pith:GOVMGIP5new · submitted 2026-06-08 · ⚛️ physics.optics · cond-mat.mes-hall· physics.chem-ph

Helicity-Resolved Spatiotemporal Mapping of Chiral Plexcitons in Helicoids

Jeong Hyun Han , Sankaran Ramesh , Jaeyeon Jo , Pavel Chabera , Ryeong Myeong Kim , Sung Hoon Cho , In Han Ha , Amitav Sahu

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Yoonsang Tak Jiawei Lv Miyoung Kim Ki Tae Nam T\"onu Pullerits

This is my paper

Pith reviewed 2026-06-27 15:51 UTC · model grok-4.3

classification ⚛️ physics.optics cond-mat.mes-hallphysics.chem-ph

keywords chiral plexcitonsgold helicoidsJ-aggregateshelicity-resolved mappingnon-Hermitian frameworkultrafast relaxationchiroptical responsespatiotemporal mapping

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The pith

Helicity of light selectively addresses distinct hybrid responses in chiral plexcitons formed by gold helicoids and J-aggregates, with gap localization accelerating relaxation.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper establishes that functionalizing intrinsically chiral gold helicoid nanoparticles with molecular J-aggregates creates chiral plexcitons. Within a non-Hermitian framework, the microscopic origin of the helicoid chiroptical response and its coupling to the excitonic transition is traced, showing how light helicity selectively drives different hybrid states. The gap-localized response is shown to enhance polarization-sensitive contrast while strengthening the local interaction, which leads to accelerated ultrafast relaxation. A sympathetic reader would care because the work positions structural chirality as a control parameter for directing energy flow in subwavelength light-matter systems on ultrafast timescales.

Core claim

Within a non-Hermitian framework, the microscopic origin of the helicoid chiroptical response and its coupling to the excitonic transition is traced, revealing how the helicity of light selectively addresses distinct hybrid responses. At the spatiotemporal extreme, the gap-localized response not only enhances polarization-sensitive contrast but also strengthens the local hybrid interaction, leading to accelerated ultrafast relaxation. Together these measurements provide a physically grounded picture of chiral plexcitonic coupling.

What carries the argument

The gap-localized response in the helicoid-plexciton system, which couples structural chirality to excitonic transitions and responds selectively to light helicity.

If this is right

Chirality acts as a practical control parameter for selectively steering nanoscale energy pathways and dynamics.
Helicity of light can address distinct hybrid responses in plexcitonic systems.
Gap localization strengthens local hybrid interactions while enhancing polarization-sensitive contrast.
Space-, time-, and polarization-resolved measurements benchmark the chiral plexcitonic coupling.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

The approach could be extended to other chiral nanoparticle shapes to test whether gap localization universally accelerates relaxation.
These results point toward possible design rules for chiral light-matter interfaces that route energy along helicity-dependent paths.
Incorporating temporal mapping with varying J-aggregate densities might isolate how coupling strength scales with the observed acceleration.

Load-bearing premise

The non-Hermitian framework combined with the chosen functionalization isolates the microscopic origin of the chiroptical response without confounding contributions from fabrication variability or additional loss channels.

What would settle it

Measurements showing identical ultrafast relaxation rates and polarization contrast for opposite light helicities, or no acceleration specifically tied to gap sites, would falsify the selective addressing and gap-localization claims.

Figures

Figures reproduced from arXiv: 2606.09097 by Amitav Sahu, In Han Ha, Jaeyeon Jo, Jeong Hyun Han, Jiawei Lv, Ki Tae Nam, Miyoung Kim, Pavel Chabera, Ryeong Myeong Kim, Sankaran Ramesh, Sung Hoon Cho, T\"onu Pullerits, Yoonsang Tak.

**Figure 1.** Figure 1: Rational design of helicoid-TDBC plexcitonic system. Schematic illustration detailing the central operating mechanisms of the individual constituents and their synergistic integration into a helicoid-TDBC plexcitonic system. In the core plasmonic helicoid (I), surface currents morphologically confined within the chiral gap induce a strong mixing of ED and MD moments and their local densities, acting as the… view at source ↗

**Figure 2.** Figure 2: Realization of helicoid-TDBC plexcitonic system. a, SEM images of helicoids, revealing distinct three-dimensional chiral gap morphologies explicitly governed by 432 rotational symmetry. b, Steady-state chiroptical spectra of the pristine helicoids, where incident polarization actively dictates the plasmonic bands’ peak wavelength, linewidth, and detuning with excitonic band. c, Electron energy loss spectro… view at source ↗

**Figure 3.** Figure 3: Macro-to-microscopic characterization of helicoid-TDBC plexcitonic coupling. a, Conceptual framework of the chiral plexcitonic interactions. (i) Multipole decomposition of the plasmonic helicoid, showing the concurrent excitation of ED and MD modes, which serves as the fundamental origin of its plasmonic chirality. (ii) Schematic illustrating the interference picture between the plasmonic continuum states … view at source ↗

**Figure 4.** Figure 4: Resolving and controlling ultrafast dynamics of helicoid-TDBC plexcitonic system. a, Schematic illustration of the custom-built transient absorption (TA) spectroscopy setup with a polarization-controlled probe pulse. b, c, Slices of TA spectra for (b) plasmonic and (c) plexcitonic helicoids, following excitation at 640 nm (pumped and probed with linear polarizations). d-f, Ultrafast decay kinetics of plasm… view at source ↗

read the original abstract

Plasmon-exciton hybrids, or plexcitons, offer deeply subwavelength light-matter interactions with versatile pathways for energy redistribution. Incorporating chirality into such systems is particularly compelling, enabling spin-sensitive optical functionality that can operate on ultrafast timescales and within ultracompact volumes. Despite recent progress in chiral plexcitonic systems, how structural chirality and plasmon-exciton coupling determine chiroptical spectra and ultrafast energy flow remains elusive. Here we realize chiral plexcitons by functionalizing intrinsically chiral gold helicoid nanoparticles with molecular J-aggregates. Within a non-Hermitian framework, we trace the microscopic origin of the helicoid chiroptical response and its coupling to the excitonic transition, revealing how the helicity of light selectively addresses distinct hybrid responses. At the spatiotemporal extreme, we find that the gap-localized response not only enhances polarization-sensitive contrast but also strengthens the local hybrid interaction, leading to accelerated ultrafast relaxation. Together, these space-, time-, and polarization-resolved measurements provide a physically grounded and experimentally benchmarked picture of chiral plexcitonic coupling, identifying chirality as a practical control parameter for selectively steering nanoscale energy pathways and dynamics.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

The paper delivers helicity-resolved maps of plexcitons in gold helicoids showing selective responses and faster relaxation, but the non-Hermitian claims rest on details not visible in the abstract.

read the letter

The main takeaway is that functionalizing chiral gold helicoids with J-aggregates produces plexcitons whose chiroptical response and ultrafast dynamics can be addressed by light helicity, with gap-localized effects apparently speeding relaxation. This is framed as filling a gap left by earlier chiral plexciton work.

What stands out as new is the combination of intrinsically chiral nanoparticles with molecular aggregates plus the space-time-polarization resolved measurements. The setup lets them track how structural chirality couples to the excitonic transition and how that affects energy flow on ultrafast scales.

The experimental realization itself looks solid on the surface: they have a concrete system and report polarization-sensitive contrast plus accelerated dynamics tied to the gap region. That gives a practical handle on chirality as a control knob.

The soft spot is the non-Hermitian framework used to trace the microscopic origin. The abstract states it reveals selective addressing and strengthened local interaction, but without the actual equations, fitting details, or raw spectra it is impossible to tell whether the model is predictive or largely descriptive. Fabrication variability in the helicoids could also introduce extra loss channels that are not obviously ruled out.

This is for groups working on nanophotonics, chiral optics, or ultrafast hybrid systems who need concrete examples of polarization control at the nanoscale. It is not yet a finished story on the theory side.

I would send it to peer review. The experimental mapping is worth referee time even if the modeling section needs tightening.

Referee Report

1 major / 0 minor

Summary. The manuscript reports the realization of chiral plexcitons via functionalization of intrinsically chiral gold helicoid nanoparticles with molecular J-aggregates. Within a non-Hermitian framework the authors trace the microscopic origin of the helicoid chiroptical response and its coupling to the excitonic transition, showing that light helicity selectively addresses distinct hybrid responses. Spatiotemporal mapping at the gap-localized extreme indicates that this localization enhances polarization-sensitive contrast, strengthens the local hybrid interaction, and produces accelerated ultrafast relaxation, thereby identifying chirality as a control parameter for nanoscale energy pathways.

Significance. If the non-Hermitian model and the experimental mapping hold, the work supplies a physically grounded, experimentally benchmarked description of chiral plexcitonic coupling. The demonstration that structural chirality can selectively steer ultrafast energy flow in deeply subwavelength volumes would be of clear interest for spin-sensitive nanophotonics and chiral optoelectronics.

major comments (1)

[Abstract] Abstract (paragraph on the non-Hermitian framework and gap-localized response): the central claim that the chosen functionalization and non-Hermitian treatment isolate the microscopic origin of the chiroptical response rests on the assumption that fabrication variability and additional loss channels do not confound the observed helicity selectivity and accelerated relaxation; without explicit controls, simulations, or error analysis this assumption remains load-bearing and unverified.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for their careful review and constructive comments. We address the single major comment below.

read point-by-point responses

Referee: [Abstract] Abstract (paragraph on the non-Hermitian framework and gap-localized response): the central claim that the chosen functionalization and non-Hermitian treatment isolate the microscopic origin of the chiroptical response rests on the assumption that fabrication variability and additional loss channels do not confound the observed helicity selectivity and accelerated relaxation; without explicit controls, simulations, or error analysis this assumption remains load-bearing and unverified.

Authors: We appreciate the referee highlighting this point. The manuscript already includes direct experimental comparisons of chiroptical spectra for bare helicoids versus J-aggregate-functionalized helicoids, as well as helicity-dependent responses, to isolate the plexcitonic contribution. The non-Hermitian framework incorporates loss channels explicitly through the imaginary parts of the gold and molecular dielectric functions. Nevertheless, to make controls more explicit, the revised manuscript will add: (i) statistical error bars and variability analysis from repeated measurements across multiple particles, (ii) electromagnetic simulations sampling geometric variations within typical fabrication tolerances, and (iii) additional control data sets. These revisions will directly verify that fabrication variability and unaccounted losses do not confound the reported helicity selectivity or accelerated relaxation. revision: yes

Circularity Check

0 steps flagged

No circularity identified; abstract-only text provides no equations or derivation chain to inspect

full rationale

The supplied document consists solely of the abstract, which summarizes experimental realizations of chiral plexcitons and invokes a non-Hermitian framework without presenting any equations, fitted parameters, self-citations, or explicit derivation steps. No load-bearing claims of the form 'X derives Y' can be examined for reduction to inputs by construction. Per the analysis rules, circularity requires quotable paper text exhibiting a specific reduction (e.g., a prediction equivalent to a fitted quantity); absent such material, the finding is no significant circularity. The central claims rest on spatiotemporal measurements and a described framework whose independence from the reported results cannot be assessed here but also cannot be flagged as circular.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Review performed on abstract only; no explicit free parameters, invented entities, or additional axioms are stated beyond the use of a non-Hermitian framework.

axioms (1)

domain assumption Non-Hermitian framework accurately captures the microscopic origin of the helicoid chiroptical response and plexciton coupling
Abstract states 'Within a non-Hermitian framework, we trace the microscopic origin...'

pith-pipeline@v0.9.1-grok · 5800 in / 1255 out tokens · 25695 ms · 2026-06-27T15:51:10.312997+00:00 · methodology

discussion (0)

Reference graph

Works this paper leans on

13 extracted references

[1]

Im, S. W. et al. Synthesis of chiral gold helicoid nanoparticles using glutathione. Nat. Protoc. 20, 1082–1096 (2025)

2025
[2]

Tatikolov, A. S. & Costa, S. M. B. Effects of normal and reverse micellar environment on the spectral properties, isomerization and aggregation of a hydrophilic cyanine dye. Chem. Phys. Lett. 346, 233– 240 (2001)

2001
[3]

Ryu, J. et al. Dimensionality reduction and unsupervised clustering for EELS-SI. Ultramicroscopy 231, 113314 (2021)

2021
[4]

& Kaivola, M

Grahn, P., Shevchenko, A. & Kaivola, M. Electromagnetic multipole theory for optical nanomaterials. New J. Phys. 14, 093033 (2012)

2012
[5]

Kim, J. W. et al. Controlling the size and circular dichroism of chiral gold helicoids. Mater. Adv. 2, 6988–6995 (2021)

2021
[6]

Han, J. H. et al. Isotropic Size Control of Chiral Gold Helicoids. J. Phys. Chem. C 129, 7020–7030 (2025)

2025
[7]

& Zhang, W

Wu, F., Li, N., Ding, B. & Zhang, W. Plasmon–Exciton Strong Coupling Effects of the Chiral Hybrid Nanostructures Based on the Plexcitonic Born–Kuhn Model. ACS Photonics 10, 1356–1366 (2023)

2023
[8]

Chiral Nanophotonics

Schäferling, M. Chiral Nanophotonics. vol. 205 (Springer, 2017)

2017
[9]

Finkelstein-Shapiro, D. et al. Understanding radiative transitions and relaxation pathways in plexcitons. Chem 7, 1092–1107 (2021)

2021
[10]

& Pullerits, T

Finkelstein-Shapiro, D., Mante, P.-A., Balci, S., Zigmantas, D. & Pullerits, T. Non-Hermitian Hamiltonians for linear and nonlinear optical response: A model for plexcitons. J. Chem. Phys. 158, 104104 (2023)

2023
[11]

Zhu, J. et al. Strong Light–Matter Interactions in Chiral Plasmonic–Excitonic Systems Assembled on DNA Origami. Nano Lett. 21, 3573–3580 (2021)

2021
[12]

Han, J. H. et al. Neural-Network-Enabled Design of a Chiral Plasmonic Nanodimer for Target- Specific Chirality Sensing. ACS Nano 17, 2306–2317 (2023)

2023
[13]

H., Ippen, E

Sun, C.-K., Vallée, F., Acioli, L. H., Ippen, E. P. & Fujimoto, J. G. Femtosecond-tunable measurement of electron thermalization in gold. Phys. Rev. B 50, 15337–15348 (1994). 14.Kim, A. S., Goswami, A., Taghinejad, M. & Cai, W. Phototransformation of achiral metasurfaces into handedness-selectable transient chiral media. Proc. Natl. Acad. Sci. 121, e23187...

1994

[1] [1]

Im, S. W. et al. Synthesis of chiral gold helicoid nanoparticles using glutathione. Nat. Protoc. 20, 1082–1096 (2025)

2025

[2] [2]

Tatikolov, A. S. & Costa, S. M. B. Effects of normal and reverse micellar environment on the spectral properties, isomerization and aggregation of a hydrophilic cyanine dye. Chem. Phys. Lett. 346, 233– 240 (2001)

2001

[3] [3]

Ryu, J. et al. Dimensionality reduction and unsupervised clustering for EELS-SI. Ultramicroscopy 231, 113314 (2021)

2021

[4] [4]

& Kaivola, M

Grahn, P., Shevchenko, A. & Kaivola, M. Electromagnetic multipole theory for optical nanomaterials. New J. Phys. 14, 093033 (2012)

2012

[5] [5]

Kim, J. W. et al. Controlling the size and circular dichroism of chiral gold helicoids. Mater. Adv. 2, 6988–6995 (2021)

2021

[6] [6]

Han, J. H. et al. Isotropic Size Control of Chiral Gold Helicoids. J. Phys. Chem. C 129, 7020–7030 (2025)

2025

[7] [7]

& Zhang, W

Wu, F., Li, N., Ding, B. & Zhang, W. Plasmon–Exciton Strong Coupling Effects of the Chiral Hybrid Nanostructures Based on the Plexcitonic Born–Kuhn Model. ACS Photonics 10, 1356–1366 (2023)

2023

[8] [8]

Chiral Nanophotonics

Schäferling, M. Chiral Nanophotonics. vol. 205 (Springer, 2017)

2017

[9] [9]

Finkelstein-Shapiro, D. et al. Understanding radiative transitions and relaxation pathways in plexcitons. Chem 7, 1092–1107 (2021)

2021

[10] [10]

& Pullerits, T

Finkelstein-Shapiro, D., Mante, P.-A., Balci, S., Zigmantas, D. & Pullerits, T. Non-Hermitian Hamiltonians for linear and nonlinear optical response: A model for plexcitons. J. Chem. Phys. 158, 104104 (2023)

2023

[11] [11]

Zhu, J. et al. Strong Light–Matter Interactions in Chiral Plasmonic–Excitonic Systems Assembled on DNA Origami. Nano Lett. 21, 3573–3580 (2021)

2021

[12] [12]

Han, J. H. et al. Neural-Network-Enabled Design of a Chiral Plasmonic Nanodimer for Target- Specific Chirality Sensing. ACS Nano 17, 2306–2317 (2023)

2023

[13] [13]

H., Ippen, E

Sun, C.-K., Vallée, F., Acioli, L. H., Ippen, E. P. & Fujimoto, J. G. Femtosecond-tunable measurement of electron thermalization in gold. Phys. Rev. B 50, 15337–15348 (1994). 14.Kim, A. S., Goswami, A., Taghinejad, M. & Cai, W. Phototransformation of achiral metasurfaces into handedness-selectable transient chiral media. Proc. Natl. Acad. Sci. 121, e23187...

1994