Should it really be that hard to model the chirality induced spin selectivity effect?

J. Fransson

arxiv: 2510.11240 · v1 · submitted 2025-10-13 · ❄️ cond-mat.mes-hall · cond-mat.str-el

Should it really be that hard to model the chirality induced spin selectivity effect?

J. Fransson This is my paper

Pith reviewed 2026-05-18 07:45 UTC · model grok-4.3

classification ❄️ cond-mat.mes-hall cond-mat.str-el

keywords chirality induced spin selectivityelectron correlationstime-reversal symmetryOnsager reciprocityspin polarizationchiral moleculesmany-body effects

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The pith

Correct modeling of the chirality induced spin selectivity effect requires electron interactions and spontaneous symmetry breaking.

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

After more than a decade of unsuccessful attempts using models without electron interactions, this review concludes that such approaches cannot explain the experimental observations of spin polarization in chiral molecules. Including interactions among electrons is essential, and this may occur through spontaneous breaking of time-reversal symmetry. This resolves potential conflicts with Onsager reciprocity, which otherwise would be violated by the observed spin selectivity. Understanding this is crucial for building microscopic theories that match the simple experimental setups.

Core claim

The paper establishes that independent-electron models fail to reproduce the chirality induced spin selectivity, so a proper theory requires electron-electron interactions. This interaction-driven approach can lead to spontaneous breaking of time-reversal symmetry, making the effect consistent with Onsager reciprocity without fundamental violations.

What carries the argument

Electron-electron interactions enabling spontaneous breaking of time-reversal symmetry in the chiral molecular setup.

If this is right

The chirality induced spin selectivity effect arises from many-body electron interactions rather than single-particle effects.
Spontaneous time-reversal symmetry breaking reconciles the observations with fundamental symmetry principles.
Effective modeling becomes possible once electron interactions are properly included in the theoretical framework.

Where Pith is reading between the lines

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

Future theoretical work should focus on developing many-body methods tailored to chiral molecular junctions.
This perspective may help explain related spin and chirality phenomena in other nanoscale systems.
Experimental probes sensitive to symmetry breaking could validate or refute the proposed role of correlations.

Load-bearing premise

The premise that failures of independent-electron models necessitate the inclusion of electron correlations to achieve the observed spin selectivity in a manner consistent with Onsager reciprocity through spontaneous symmetry breaking.

What would settle it

An experiment showing clear evidence of time-reversal symmetry breaking, for instance through asymmetric transport properties or induced magnetic fields in the absence of external magnetism, would support the claim; lack of such evidence in detailed measurements would challenge it.

read the original abstract

The chirality induced spin selectivity effect remains a challenge to capture with theoretical modeling. While at least a decade was spent on independent electron models, which completely fail to reproduce the experimental results, the lesson to be drawn out of these efforts is that a correct modeling of the effect has to include interactions among the electrons. In the discussion of the phenomenon ones inevitably encounters the Onsager reciprocity and time-reversal symmetry, and questions whether the observations violate these fundamental concepts, or whether we have not been able to identify what it is that make those concepts redundant in this context. The experimental fact is that electrons spin-polarize by one or another reason, when traversing chiral molecules. The set-ups are simple enough to enable effective modeling, however, overcoming the grand failures of the theoretical efforts, thus far, and formulating a theory which is founded on microscopic modeling appears to be a challenge. A discussion of the importance of electron correlations is outlined, pointing to possible spontaneous breaking of time-reversal symmetry and Onsager reciprocity.

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

Fransson's perspective notes that single-particle models have failed for a decade on CISS and calls for electron correlations possibly via spontaneous TRS breaking, but supplies no mechanism or check.

read the letter

The main thing to know is that this is a perspective arguing independent-electron models have not worked for chirality-induced spin selectivity despite a decade of effort, so any viable theory needs electron interactions and may require spontaneous breaking of time-reversal symmetry to remain consistent with Onsager reciprocity. The paper states this lesson plainly and correctly flags the tension between observed spin polarization in chiral molecules and fundamental symmetry principles. It does a reasonable job summarizing why the experimental setups look simple enough for modeling yet theory has lagged. The observation that non-interacting pictures fall short is fair and aligns with what many in the field have noted. The soft spot is that the argument stays general. No specific interaction term appears, no channel for symmetry breaking is derived, and there is no check on whether such breaking would stay stable in finite non-magnetic molecules without producing net magnetization or clashing with other linear-response tests already done on these systems. The suggestion of spontaneous breaking is introduced to reconcile the data with principles, but it functions more as a pointer than a worked proposal. This piece is aimed at theorists already working on molecular spintronics or CISS who are looking for a new direction after mean-field approaches stalled. A reader wanting a concrete Hamiltonian, numerical results, or falsifiable prediction will not find them. The work shows clear engagement with the modeling literature and the symmetry issues, so it deserves a serious referee even if the symmetry-breaking idea needs more development to become convincing. I would send it for peer review rather than desk reject, especially if the journal takes perspectives, with the expectation that referees will ask for a more explicit mechanism.

Referee Report

2 major / 2 minor

Summary. The manuscript argues that independent-electron models have failed to capture the chirality-induced spin selectivity (CISS) effect over the past decade, implying that electron-electron interactions must be included in any correct theory. It raises questions about consistency with Onsager reciprocity and time-reversal symmetry, and suggests that spontaneous breaking of time-reversal symmetry induced by correlations could reconcile the experimental observations of spin polarization in chiral molecules with fundamental principles.

Significance. If the central perspective holds, the work could usefully redirect theoretical efforts in the CISS field away from single-particle approaches toward correlated models. However, the manuscript offers no new derivation, Hamiltonian, or quantitative benchmark, so its significance rests entirely on whether the proposed symmetry-breaking scenario can be made concrete and testable.

major comments (2)

[Abstract / main discussion paragraph] The central claim that independent-electron models 'completely fail' and that interactions are therefore required is presented without any specific counter-example Hamiltonian, numerical result, or reference to a particular failed calculation (see abstract and the paragraph beginning 'The experimental fact is...'). This makes the inference to spontaneous TRS breaking load-bearing yet unsupported by explicit modeling.
[Discussion of Onsager reciprocity and TRS] The suggestion of spontaneous time-reversal symmetry breaking to preserve Onsager reciprocity is introduced without identifying a microscopic mechanism (e.g., a Hubbard term, spin-orbit-assisted pairing, or mean-field channel) or demonstrating stability in finite, non-magnetic chiral molecules. No consistency check against existing linear-response data or net-magnetization constraints is provided.

minor comments (2)

[Abstract] The phrase 'at least a decade' should be replaced by a precise citation to the earliest independent-electron CISS calculations referenced.
[Paragraph on fundamental concepts] Notation for 'Onsager reciprocity' and 'time-reversal symmetry' is used without defining the relevant linear-response coefficients or the precise symmetry operation being broken.

Simulated Author's Rebuttal

2 responses · 1 unresolved

We thank the referee for the constructive and insightful comments on our perspective manuscript. We agree that greater specificity in referencing prior modeling efforts and clearer framing of the proposed symmetry-breaking scenario would strengthen the paper. We address each major comment below and indicate the revisions we will make.

read point-by-point responses

Referee: The central claim that independent-electron models 'completely fail' and that interactions are therefore required is presented without any specific counter-example Hamiltonian, numerical result, or reference to a particular failed calculation (see abstract and the paragraph beginning 'The experimental fact is...'). This makes the inference to spontaneous TRS breaking load-bearing yet unsupported by explicit modeling.

Authors: We acknowledge that the manuscript is a perspective piece rather than a technical calculation paper and does not introduce a new Hamiltonian or numerical benchmark. The statement draws from the accumulated literature over the past decade, in which a range of independent-electron models (tight-binding with spin-orbit coupling, helical electrostatic potentials, and scattering approaches) have been unable to reproduce the large, robust spin polarizations observed experimentally. To address the concern, we will revise the abstract and the relevant discussion paragraph to replace the phrasing 'completely fail' with 'have not succeeded in quantitatively reproducing the magnitude and robustness of the observed effect.' We will also add explicit citations to representative independent-electron studies that illustrate these limitations. This revision clarifies that our inference to the need for correlations is based on the pattern in the existing literature rather than on a new explicit counter-example within this work. revision: yes
Referee: The suggestion of spontaneous time-reversal symmetry breaking to preserve Onsager reciprocity is introduced without identifying a microscopic mechanism (e.g., a Hubbard term, spin-orbit-assisted pairing, or mean-field channel) or demonstrating stability in finite, non-magnetic chiral molecules. No consistency check against existing linear-response data or net-magnetization constraints is provided.

Authors: We agree that identifying a concrete microscopic mechanism and performing stability or consistency checks would make the suggestion more actionable. Because the manuscript is a perspective whose purpose is to highlight open questions and redirect theoretical effort, we present spontaneous TRS breaking as a possible conceptual resolution rather than a derived result. In the revision we will expand the discussion to outline candidate mechanisms (for example, correlation-driven mean-field order enabled by the chiral geometry) and note that any such order could be local or transport-induced, thereby remaining compatible with zero net magnetization in equilibrium. We will also add a brief paragraph addressing consistency with Onsager relations in the non-equilibrium transport regime. A full microscopic derivation, numerical demonstration of stability in finite molecules, and direct comparison with linear-response data lie beyond the scope of a perspective article and would constitute a separate research project. revision: partial

standing simulated objections not resolved

A complete microscopic Hamiltonian together with numerical evidence demonstrating spontaneous TRS breaking and its stability in finite non-magnetic chiral molecules; such a calculation would require a dedicated computational study outside the perspective format of the present manuscript.

Circularity Check

0 steps flagged

No circularity: discussion of modeling failures does not reduce to self-defined inputs

full rationale

The paper is a discussion piece reviewing the repeated failure of independent-electron models to capture the chirality-induced spin selectivity effect and concluding that electron interactions must be included, with a suggestion of possible spontaneous time-reversal symmetry breaking to address Onsager reciprocity. No mathematical derivation, equations, fitted parameters, or first-principles predictions are presented that could reduce to the paper's own inputs by construction. The central lesson is drawn from external experimental observations and the shortcomings of prior independent-electron approaches rather than from any self-referential definition, self-citation load-bearing premise, or ansatz smuggled via prior work. The argument remains self-contained against external benchmarks without internal circular reduction.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 1 invented entities

The central claim rests on the domain assumption that electron interactions can induce effective symmetry breaking without external fields or explicit mechanisms.

axioms (1)

domain assumption Time-reversal symmetry and Onsager reciprocity are normally conserved but can be spontaneously broken in interacting chiral systems.
Invoked to argue that observations need not violate fundamental concepts.

invented entities (1)

Spontaneous breaking of time-reversal symmetry induced by electron correlations no independent evidence
purpose: To reconcile large CISS with Onsager reciprocity.
Proposed as possible resolution but without independent evidence or explicit model.

pith-pipeline@v0.9.0 · 5702 in / 1218 out tokens · 37207 ms · 2026-05-18T07:45:56.051369+00:00 · methodology

discussion (0)

Lean theorems connected to this paper

Citations machine-checked in the Pith Canon. Every link opens the source theorem in the public Lean library.

IndisputableMonolith/Foundation/ArrowOfTime.lean arrow_from_z unclear

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unclear
Relation between the paper passage and the cited Recognition theorem.

the lesson to be drawn out of these efforts is that a correct modeling of the effect has to include interactions among the electrons... pointing to possible spontaneous breaking of time-reversal symmetry and Onsager reciprocity
IndisputableMonolith/Foundation/AbsoluteFloorClosure.lean reality_from_one_distinction unclear

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unclear
Relation between the paper passage and the cited Recognition theorem.

non-interacting channels cannot spontaneously give rise to spin-polarized transport... Spontaneous formation of spin-polarization and magnetism requires interactions between the electrons

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