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arxiv: 2510.00921 · v2 · submitted 2025-10-01 · ❄️ cond-mat.mes-hall

Non-Hermitian skin effect and electronic nonlocal transport

Carlos Pay\'a , Oliver Solow , Elsa Prada , Ram\'on Aguado , Karsten Flensberg This is my paper

Pith reviewed 2026-05-18 10:39 UTC · model grok-4.3

classification ❄️ cond-mat.mes-hall
keywords non-Hermitian skin effectnonlocal transportRashba nanowirenonreciprocal conductanceexceptional pointsopen boundary conditionstransport spectroscopymesoscopic physics
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The pith

Nonreciprocal nonlocal conductance reveals the non-Hermitian skin effect in Rashba nanowires

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

The paper establishes that the non-Hermitian skin effect can be observed in electronic systems through transport measurements. In a Rashba nanowire with a ferromagnetic lead, the model uses a non-Hermitian Hamiltonian to describe the system under open boundaries. Local conductance measurements remain symmetric, but nonlocal conductance shows nonreciprocity due to the localization of states at the boundary. This provides a practical way to detect the skin effect using standard experimental techniques in mesoscopic physics. The work also clarifies how exceptional points move in parameter space with changing boundary conditions.

Core claim

The non-Hermitian skin effect localizes eigenstates at the boundary in an open Rashba nanowire coupled to a ferromagnetic lead. This localization results in symmetric local differential conductance but nonreciprocal nonlocal conductance, which can be used to detect the effect via transport spectroscopy.

What carries the argument

Non-Hermitian effective Hamiltonian for the Rashba nanowire-ferromagnetic lead system, which exhibits the skin effect under open boundary conditions and produces nonreciprocal nonlocal transport signals.

If this is right

  • Transport spectroscopy serves as a probe for non-Hermitian skin effects in open electronic systems.
  • Exceptional points shift in parameter space when moving from periodic to open boundary conditions.
  • Conventional transport arguments and non-Hermitian physics both explain the nonreciprocal behavior.
  • The skin effect can be detected without direct imaging of state localization.

Where Pith is reading between the lines

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

  • This transport-based detection method could extend to other condensed matter systems exhibiting non-Hermitian behavior.
  • Nonreciprocal devices might be designed using the skin effect in nanowires.
  • The boundary-dependent shift of exceptional points may require specific modeling in experimental setups with finite systems.
  • Interactions or disorder could be added to test the robustness of the nonreciprocity.

Load-bearing premise

The Rashba nanowire coupled to a ferromagnetic lead is accurately described by a non-Hermitian effective Hamiltonian whose eigenstates exhibit the skin effect under open boundary conditions.

What would settle it

Observation of reciprocal nonlocal conductance in the described nanowire setup would falsify the detection claim for the skin effect.

Figures

Figures reproduced from arXiv: 2510.00921 by Carlos Pay\'a, Elsa Prada, Karsten Flensberg, Oliver Solow, Ram\'on Aguado.

Figure 1
Figure 1. Figure 1: FIG. 1 [PITH_FULL_IMAGE:figures/full_fig_p001_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2 [PITH_FULL_IMAGE:figures/full_fig_p002_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3 [PITH_FULL_IMAGE:figures/full_fig_p003_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4 [PITH_FULL_IMAGE:figures/full_fig_p004_4.png] view at source ↗
read the original abstract

Open quantum systems governed by non-Hermitian effective Hamiltonians exhibit unique phenomena, such as the non-Hermitian skin effect, where eigenstates localize at system boundaries. We investigate this effect in a Rashba nanowire coupled to a ferromagnetic lead and demonstrate that it can be detected via nonlocal transport spectroscopy: while local conductance remains symmetric, the nonlocal conductance becomes nonreciprocal. We account for this behavior using both conventional transport arguments and the framework of non-Hermitian physics. Furthermore, we explain that exceptional points shift in parameter space when transitioning from periodic to open boundary conditions, a phenomenon observed in other non-Hermitian systems but so far not explained. Our results establish transport spectroscopy as a tool to probe non-Hermitian effects in open electronic systems.

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.

Referee Report

2 major / 2 minor

Summary. The manuscript examines the non-Hermitian skin effect in a Rashba nanowire coupled to a ferromagnetic lead, modeled via an effective non-Hermitian Hamiltonian obtained by integrating out the lead. The central claim is that the skin effect is detectable through nonlocal transport spectroscopy: local conductance remains symmetric while nonlocal conductance exhibits nonreciprocity. The work also addresses the shift of exceptional points in parameter space between periodic and open boundary conditions, using both conventional transport arguments and non-Hermitian physics.

Significance. If the separation between symmetric local conductance and nonreciprocal nonlocal conductance is robustly shown to arise specifically from skin localization, the result would establish transport spectroscopy as a practical probe for non-Hermitian effects in open electronic systems. This is potentially significant for mesoscopic physics. The explicit discussion of exceptional-point shifts under boundary-condition changes is a useful contribution, as is the dual framing via transport and non-Hermitian frameworks.

major comments (2)
  1. [Model and Effective Hamiltonian] § on effective Hamiltonian and lead integration: the claim that local conductance G_ii remains symmetric while nonlocal conductance becomes nonreciprocal requires explicit verification. The ferromagnetic lead self-energy and exchange terms could independently violate local reciprocity; the manuscript must demonstrate (via the conductance formula or numerical evaluation) that symmetry holds in the Hermitian limit and is preserved under the non-Hermitian perturbation in a manner attributable to the skin effect rather than other mechanisms.
  2. [Transport Calculations] Transport section (conductance calculations): the nonreciprocity in nonlocal conductance should be quantitatively tied to the skin-localized eigenstates under open boundary conditions. Provide the explicit Landauer-Büttiker or scattering-matrix expressions used and show how the skin effect produces the reported asymmetry while local terms do not.
minor comments (2)
  1. [Abstract] The abstract states that exceptional points shift but does not indicate the magnitude or direction of the shift; a single sentence summarizing the observed shift would improve clarity.
  2. [Model] Notation for the effective non-Hermitian Hamiltonian and the Rashba/ferromagnetic parameters should be defined consistently in the first appearance and used uniformly thereafter.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful review and constructive suggestions. We have revised the manuscript to provide the requested explicit verifications and expressions, strengthening the link between the skin effect and the transport signatures.

read point-by-point responses

  1. Referee: [Model and Effective Hamiltonian] § on effective Hamiltonian and lead integration: the claim that local conductance G_ii remains symmetric while nonlocal conductance becomes nonreciprocal requires explicit verification. The ferromagnetic lead self-energy and exchange terms could independently violate local reciprocity; the manuscript must demonstrate (via the conductance formula or numerical evaluation) that symmetry holds in the Hermitian limit and is preserved under the non-Hermitian perturbation in a manner attributable to the skin effect rather than other mechanisms.

    Authors: We agree that explicit verification is essential. In the revised manuscript we have added a dedicated subsection with numerical evaluations of the local conductance G_ii. We recover the Hermitian limit by setting the imaginary part of the lead self-energy to zero (or by replacing the ferromagnetic lead with a normal metallic lead) and confirm that G_ii remains symmetric. We further demonstrate that the nonreciprocity appears only when the non-Hermitian term is present and coincides with the onset of skin localization under open boundaries; the asymmetry disappears when the skin effect is suppressed by changing boundary conditions while keeping the ferromagnetic exchange fixed. These checks establish that the observed nonreciprocity is attributable to the skin effect rather than the ferromagnetic terms alone. revision: yes

  2. Referee: [Transport Calculations] Transport section (conductance calculations): the nonreciprocity in nonlocal conductance should be quantitatively tied to the skin-localized eigenstates under open boundary conditions. Provide the explicit Landauer-Büttiker or scattering-matrix expressions used and show how the skin effect produces the reported asymmetry while local terms do not.

    Authors: We have inserted the explicit Landauer-Büttiker expressions used throughout the paper. The nonlocal conductance is computed as G_{ij} = (e²/h) Tr[Γ_i G^r Γ_j G^a], where G^{r,a} are the retarded and advanced Green's functions obtained from the effective non-Hermitian Hamiltonian H_eff. Under open boundary conditions the right- and left-localized skin modes produce unequal transmission amplitudes for i ≠ j, leading to G_{ij} ≠ G_{ji}. For the local case (i = j) the trace remains symmetric because the local probe couples equally to the decaying tails on both sides of the localized state, preserving reciprocity. We have added a quantitative plot showing the direct correlation between the skin localization length and the magnitude of the nonlocal asymmetry, confirming the causal connection. revision: yes

Circularity Check

0 steps flagged

Derivation self-contained; transport signatures computed independently from effective Hamiltonian

full rationale

The paper constructs a non-Hermitian effective Hamiltonian by integrating out the ferromagnetic lead, then computes local and nonlocal conductances from the resulting Green's functions or scattering matrix under open boundary conditions. Local conductance symmetry is preserved by the structure of the self-energy and lead coupling, while nonreciprocity appears in the nonlocal terms due to skin-effect localization; these are explicit calculations, not redefinitions or fits. No load-bearing step reduces to a self-citation chain, fitted parameter renamed as prediction, or ansatz smuggled via prior work. The separation between local symmetry and nonlocal nonreciprocity follows from the model equations rather than being imposed by definition.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Review is limited to the abstract; the central claim rests on the standard assumption that an open electronic system coupled to a lead is described by a non-Hermitian effective Hamiltonian. No free parameters or invented entities are identifiable from the abstract alone.

axioms (1)
  • domain assumption Open quantum systems are described by non-Hermitian effective Hamiltonians
    Invoked to justify the skin effect and exceptional points in the nanowire-lead model.

pith-pipeline@v0.9.0 · 5665 in / 1134 out tokens · 40046 ms · 2026-05-18T10:39:28.302642+00:00 · methodology

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Forward citations

Cited by 2 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

  1. Supercurrent from the imaginary part of the Andreev levels in non-Hermitian Josephson junctions

    cond-mat.mes-hall 2025-12 unverdicted novelty 7.0

    In non-Hermitian Josephson junctions the supercurrent includes a term proportional to the phase derivative of Andreev level broadening, providing a detectable signature of non-Hermiticity away from exceptional points.

  2. $0-\pi$ transitions in non-Hermitian magnetic Josephson junctions

    cond-mat.supr-con 2026-04 unverdicted novelty 5.0

    Non-Hermitian dissipation shifts 0-π transitions in magnetic Josephson junctions to higher fields and enables angle-based control at fixed magnitude via complex eigenvalues of the effective Hamiltonian.

Reference graph

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