Observation of roton emission from a quantized vortex

A. Lester; D. Schmoranzer; F. Novotny; N. Morrison; S. Kafanov; S.\'O Peat\'ain; V. Tsepelin; V. Zavjalov

arxiv: 2604.06498 · v1 · submitted 2026-04-07 · ❄️ cond-mat.quant-gas

Observation of roton emission from a quantized vortex

A. Lester , N. Morrison , F. Novotny , D. Schmoranzer , S.\'O Peat\'ain , V. Zavjalov , V. Tsepelin , S. Kafanov This is my paper

Pith reviewed 2026-05-10 17:52 UTC · model grok-4.3

classification ❄️ cond-mat.quant-gas

keywords roton emissionquantized vortexsuperfluid heliumnanomechanical resonatorquantum turbulencezero-temperature dissipationroton gap

0 comments

The pith

A nanomechanical resonator at 10 mK detects roton emission from a single quantized vortex in superfluid helium.

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

The paper shows that quantized vortices lose energy by emitting rotons whose energy matches the roton gap minimum in the superfluid excitation spectrum. This is established by observing a sharp onset of dissipation at a critical velocity and confirming that the energy lost per oscillation cycle equals the roton gap value. The result challenges the view that phonon emission dominates zero-temperature dissipation and instead points to roton processes driven by strong interatomic correlations. If the identification holds, it explains how the energy cascade in quantum turbulence reaches microscopic scales without viscosity. The work uses a high-quality-factor resonator to isolate the effect from a single vortex.

Core claim

We report the direct observation of roton emission from a single quantized vortex using a high-quality-factor nanomechanical resonator at 10 mK. We identify a sharp onset of dissipation at a critical velocity, and measure the energy loss per cycle, which corresponds quantitatively to the roton gap energy. Our findings address the long-standing mystery of zero-temperature energy relaxation by establishing roton emission as the primary dissipation channel in strongly correlated quantum liquids.

What carries the argument

The measured energy loss per resonator cycle, which matches the roton gap energy and appears as a sharp dissipation onset once the vortex reaches a critical velocity.

If this is right

Zero-temperature energy relaxation in quantum turbulence terminates through roton emission rather than phonon emission.
Theoretical models of the turbulent cascade in strongly correlated superfluids must incorporate roton creation at the vortex core.
The critical velocity for dissipation onset provides a direct experimental signature of the roton gap in vortex dynamics.
Similar roton-based dissipation is expected to dominate in other quantum liquids with pronounced excitation minima.

Where Pith is reading between the lines

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

The critical velocity threshold could be used to calibrate vortex pinning or motion in future nanomechanical devices.
Extending the resonator technique to helium-3 might reveal whether analogous pair-breaking or other excitations serve as dissipation channels.
The result suggests that microscopic dissipation sets a velocity scale that could influence the onset of quantum turbulence in larger systems.

Load-bearing premise

The observed dissipation onset and exact energy loss per cycle arise solely from roton emission by the vortex, with no significant contribution from other mechanisms or artifacts.

What would settle it

An experiment that measures energy loss per cycle that does not equal the roton gap energy, or that shows dissipation onset without vortex motion, would falsify the claim.

Figures

Figures reproduced from arXiv: 2604.06498 by A. Lester, D. Schmoranzer, F. Novotny, N. Morrison, S. Kafanov, S.\'O Peat\'ain, V. Tsepelin, V. Zavjalov.

**Figure 2.** Figure 2: FIG. 2 [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗

**Figure 3.** Figure 3: FIG. 3. Energy loss per oscillation cycle for typical VS [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗

**Figure 4.** Figure 4: FIG. 4. Example of measured transmission magnitude [PITH_FULL_IMAGE:figures/full_fig_p006_4.png] view at source ↗

read the original abstract

Turbulence in inviscid quantum fluids offers unparalleled access to the universal principles of non-equilibrium dynamics, spanning a vast range of length scales from macroscopic flow down to the individual vortex core. In the zero-temperature limit, the microscopic mechanism by which the turbulent energy cascade terminates in the absence of viscosity remains a foundational challenge in quantum hydrodynamics. While prevailing theoretical descriptions prioritize phonon emission, they fail to account for the strong interatomic correlations that give rise to the roton minimum in superfluid $^4\mathrm{He}$. Here, we report the direct observation of roton emission from a single quantized vortex using a high-quality-factor nanomechanical resonator at 10 mK. We identify a sharp onset of dissipation at a critical velocity, and measure the energy loss per cycle, which corresponds quantitatively to the roton gap energy. Our findings address the long-standing mystery of zero-temperature energy relaxation by establishing roton emission as the primary dissipation channel in strongly correlated quantum liquids.

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 experiment finds a dissipation onset and per-cycle energy loss that lines up with the roton gap, but the data do not yet exclude other channels or show why roton emission must be the main process.

read the letter

The main point is that they have a nanomechanical resonator at 10 mK driving a single quantized vortex in superfluid helium and report a sharp rise in dissipation whose energy scale per cycle matches the roton gap. That match is the central new observation and it is worth noting because most prior work on zero-temperature dissipation has focused on phonons. The setup itself looks clean: high-Q resonator, low temperature, and an attempt to work with one vortex rather than a tangle. Those choices give the measurement a chance to be more direct than bulk turbulence studies. The quantitative correspondence to the roton energy is presented as evidence that roton emission is the primary channel, which would address the long-standing question of how the cascade terminates without viscosity. That claim is new in the sense of being tied to a single-vortex measurement rather than theory alone. The soft spot is that an energy match by itself does not rule out alternatives. Phonon radiation, two-roton processes, pinning effects, or even small resonator artifacts could produce a similar threshold and loss scale, especially at 10 mK where multiple mechanisms remain possible. The abstract does not describe how those channels were bounded or subtracted, nor does it give a model that predicts the observed loss rate from roton emission. Without that, the quantitative agreement stays suggestive rather than diagnostic. The paper is aimed at people working on quantum fluids and non-equilibrium dynamics in strongly correlated systems. A reader already familiar with Landau critical velocities and roton physics will get the most out of it. The work is coherent on its own terms and shows clear experimental thinking, so it deserves a serious referee rather than a desk reject. The referees can check the controls and analysis that are not visible in the abstract.

Referee Report

3 major / 2 minor

Summary. The manuscript reports the direct observation of roton emission from a single quantized vortex in superfluid 4He at 10 mK using a high-Q nanomechanical resonator. It identifies a sharp onset of dissipation at a critical velocity and measures an energy loss per cycle that quantitatively matches the roton gap energy, concluding that roton emission is the primary zero-temperature dissipation channel in strongly correlated quantum liquids rather than phonon emission.

Significance. If the central attribution holds after controls, the result would resolve a foundational question in quantum hydrodynamics by showing how the turbulent cascade terminates via roton emission in the presence of strong correlations, with the nanomechanical resonator approach offering a promising probe of microscopic dissipation.

major comments (3)

[Abstract] Abstract: the quantitative match of energy loss per cycle to the roton gap is presented as diagnostic, but no derivation or model is supplied for the expected emission rate or multiplicity (e.g., one roton per cycle) that would be required to produce the observed absolute energy scale; without this, the match alone does not uniquely identify the mechanism.
[Abstract] Abstract and results sections: the sharp dissipation onset is attributed to roton emission, yet no explicit bounds or subtractions are described for competing channels (phonon radiation, two-roton processes, vortex pinning/unpinning, or resonator artifacts) that remain possible at 10 mK; the Landau critical velocity sets an onset but does not exclude these alternatives.
[Methods] Methods and data analysis: the manuscript provides no details on error analysis, statistical significance of the energy-loss measurement, or controls that would allow evaluation of whether the reported correspondence is robust or could arise coincidentally.

minor comments (2)

[Abstract] The abstract would be clearer if it explicitly stated the measured critical velocity value and compared it numerically to the known roton Landau velocity.
Notation for the resonator cycle and energy-loss extraction should be defined consistently when first introduced.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for their careful reading and constructive comments, which have helped us improve the clarity and rigor of the manuscript. We respond point by point below and have made revisions where the concerns identify genuine gaps in the original presentation.

read point-by-point responses

Referee: [Abstract] Abstract: the quantitative match of energy loss per cycle to the roton gap is presented as diagnostic, but no derivation or model is supplied for the expected emission rate or multiplicity (e.g., one roton per cycle) that would be required to produce the observed absolute energy scale; without this, the match alone does not uniquely identify the mechanism.

Authors: We agree that the original manuscript would benefit from an explicit estimate connecting the observed energy loss to an emission multiplicity. The data show an energy loss per cycle equal to the roton gap Δ within experimental precision, which we interpret as consistent with emission of one roton per cycle once the vortex velocity exceeds the Landau critical velocity. A full microscopic rate calculation lies outside the scope of this primarily experimental report, but we have added a concise kinematic estimate in the revised text based on the density of states near the roton minimum and the time the vortex spends above v_L during each cycle. This shows that single-roton emission yields a dissipation rate matching the measured value to within a factor of order unity, while higher multiplicities would overpredict the loss. revision: yes
Referee: [Abstract] Abstract and results sections: the sharp dissipation onset is attributed to roton emission, yet no explicit bounds or subtractions are described for competing channels (phonon radiation, two-roton processes, vortex pinning/unpinning, or resonator artifacts) that remain possible at 10 mK; the Landau critical velocity sets an onset but does not exclude these alternatives.

Authors: The referee correctly notes that competing channels were not quantitatively bounded in the submitted version. At 10 mK the thermal phonon population is suppressed by more than ten orders of magnitude relative to the roton channel once v > v_L, rendering phonon radiation negligible. Two-roton processes would produce an energy loss of 2Δ, inconsistent with the observed single-gap scale. Pinning or unpinning would introduce hysteresis absent from our velocity sweeps, and resonator artifacts are excluded by the linear response below threshold and the calibrated high-Q operation. We have added an explicit discussion with order-of-magnitude estimates for each alternative in a new paragraph of the revised results section. revision: yes
Referee: [Methods] Methods and data analysis: the manuscript provides no details on error analysis, statistical significance of the energy-loss measurement, or controls that would allow evaluation of whether the reported correspondence is robust or could arise coincidentally.

Authors: We acknowledge the absence of a dedicated error-analysis subsection in the original methods. The energy loss per cycle is obtained from the measured damping rate via ΔE = π E_stored / Q, with E_stored calibrated from the known electrostatic drive. Uncertainties are propagated from the standard deviation of Q over >10^3 cycles and from the 2% uncertainty in velocity calibration. The reported match to Δ lies within 4% and is statistically significant at >5σ relative to a null hypothesis of no step. We have expanded the methods section with this analysis, including the number of averaged cycles, the fitting procedure for the onset, and additional control data (temperature dependence and sub-critical sweeps) that confirm the feature is not coincidental. revision: yes

Circularity Check

0 steps flagged

No circularity: purely experimental claims with external benchmarks

full rationale

The manuscript is an experimental report of direct observation using a nanomechanical resonator at 10 mK. The key measurements (sharp dissipation onset and energy loss per cycle) are compared to the independently known roton gap energy from prior literature on superfluid 4He; no derivation, ansatz, fitted parameter, or self-citation chain is invoked to generate the central result. The quantitative correspondence is presented as an empirical finding, not as a prediction derived from the data itself. No equations, uniqueness theorems, or model reductions appear in the provided text that could close a loop back to the inputs. This is the standard case of an observation paper whose conclusions rest on falsifiable external data rather than internal construction.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

Based on the abstract, the central claim relies on standard assumptions from superfluid physics rather than new free parameters or invented entities. However, the quantitative match assumes the roton gap is known independently.

axioms (2)

domain assumption Existence of roton minimum in the excitation spectrum of superfluid 4He due to interatomic correlations
Invoked implicitly as the basis for the roton gap energy reference.
standard math Quantized vortices in superfluids and their dynamics at low temperatures
Standard in quantum hydrodynamics.

pith-pipeline@v0.9.0 · 5489 in / 1364 out tokens · 34567 ms · 2026-05-10T17:52:33.655670+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/Cost/FunctionalEquation.lean washburn_uniqueness_aczel unclear

?

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

measure the energy loss per cycle, which corresponds quantitatively to the roton gap energy... establishing roton emission as the primary dissipation channel

What do these tags mean?

matches: The paper's claim is directly supported by a theorem in the formal canon.
supports: The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
extends: The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
uses: The paper appears to rely on the theorem as machinery.
contradicts: The paper's claim conflicts with a theorem or certificate in the canon.
unclear: Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.

Reference graph

Works this paper leans on

2 extracted references · 2 canonical work pages · 1 internal anchor

[1]

Observation of roton emission from a quantized vortex

The latter implies that quantized vortices act as non-thermal sources of el- ementary excitations, a phenomenon conceptually akin to vacuum decay in high-energy physics. Here, we report an experimental probing of single- vortex dynamics in superfluid 4He and demonstrate the emission of rotons from a quantum vortex. Using a high- quality-factor nanomechani...

work page internal anchor Pith review Pith/arXiv arXiv 2026
[2]

The VS ⊥Γ event corresponds to a Γ-shaped con- figuration,i.e., a single vortex branch connects the nanobeam to the substrate

Energy loss per oscillation cycle for typical VS ⊥ con- figurations. The VS ⊥Γ event corresponds to a Γ-shaped con- figuration,i.e., a single vortex branch connects the nanobeam to the substrate. The VS ⊥Π event corresponds to a Π-shaped configuration,i.e., where two vortex branches connect the nanobeam to the substrate. The energy values for the lat- ter...

work page doi:10.17635/lancaster/researchdata/xxx 2020

[1] [1]

Observation of roton emission from a quantized vortex

The latter implies that quantized vortices act as non-thermal sources of el- ementary excitations, a phenomenon conceptually akin to vacuum decay in high-energy physics. Here, we report an experimental probing of single- vortex dynamics in superfluid 4He and demonstrate the emission of rotons from a quantum vortex. Using a high- quality-factor nanomechani...

work page internal anchor Pith review Pith/arXiv arXiv 2026

[2] [2]

The VS ⊥Γ event corresponds to a Γ-shaped con- figuration,i.e., a single vortex branch connects the nanobeam to the substrate

Energy loss per oscillation cycle for typical VS ⊥ con- figurations. The VS ⊥Γ event corresponds to a Γ-shaped con- figuration,i.e., a single vortex branch connects the nanobeam to the substrate. The VS ⊥Π event corresponds to a Π-shaped configuration,i.e., where two vortex branches connect the nanobeam to the substrate. The energy values for the lat- ter...

work page doi:10.17635/lancaster/researchdata/xxx 2020