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arxiv: 2406.17569 · v1 · submitted 2024-06-25 · ❄️ cond-mat.quant-gas · cond-mat.stat-mech

Characterising transport in a quantum gas by measuring Drude weights

Philipp Sch\"uttelkopf , Mohammadamin Tajik , Nataliia Bazhan , Federica Cataldini , Si-Cong Ji , J\"org Schmiedmayer , Frederik M{\o}ller This is my paper

Pith reviewed 2026-05-24 00:19 UTC · model grok-4.3

classification ❄️ cond-mat.quant-gas cond-mat.stat-mech
keywords Drude weightquantum gasone-dimensional bosonsintegrabilityhydrodynamic theorytransport propertiesultracold atomsdissipationless transport
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The pith

Drude weights show that transport in an integrable one-dimensional quantum gas is almost fully dissipationless even at finite temperatures and interactions.

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

The paper measures the Drude weights in an ultracold gas of interacting bosonic atoms confined to one dimension, quantifying the ballistic atomic and energy currents induced by external perturbations. Currents are generated via two protocols: applying a constant force and joining subsystems prepared in different equilibrium states. Integrability ensures that dynamics are carried by ballistically propagating, long-lived quasi-particle excitations, so that Drude weights almost fully characterise large-scale transport. The measured values align with predictions from a hydrodynamic theory, confirming nearly dissipationless behavior at finite temperatures and interactions.

Core claim

By measuring Drude weights of atomic and energy currents in a one-dimensional ultracold bosonic gas, the transport is shown to be almost fully dissipationless, in agreement with hydrodynamic theory, because integrability produces ballistically propagating long-lived quasi-particle excitations that govern the dynamics even at finite temperatures and interactions.

What carries the argument

The Drude weight, which quantifies the ballistic component of transport for atomic and energy currents induced by external potentials.

Load-bearing premise

Integrability causes the dynamics to be governed by ballistically propagating, long-lived quasi-particle excitations so that Drude weights almost fully characterise large-scale transport.

What would settle it

A measurement showing substantial dissipative currents or clear deviations from the hydrodynamic Drude-weight predictions at the experimental temperatures and interaction strengths would falsify the claim of almost fully dissipationless transport.

Figures

Figures reproduced from arXiv: 2406.17569 by Federica Cataldini, Frederik M{\o}ller, J\"org Schmiedmayer, Mohammadamin Tajik, Nataliia Bazhan, Philipp Sch\"uttelkopf, Si-Cong Ji.

Figure 1
Figure 1. Figure 1: FIG. 1 [PITH_FULL_IMAGE:figures/full_fig_p002_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 ↗
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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 ↗
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Figure 5. Figure 5: FIG. 5 [PITH_FULL_IMAGE:figures/full_fig_p007_5.png] view at source ↗
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Figure 6. Figure 6: FIG. 6 [PITH_FULL_IMAGE:figures/full_fig_p008_6.png] view at source ↗
read the original abstract

Transport properties play a crucial role in defining materials as insulators, metals, or superconductors. A fundamental parameter in this regard is the Drude weight, which quantify the ballistic transport of charge carriers. In this work, we measure the Drude weights of an ultracold gas of interacting bosonic atoms confined to one dimension, characterising the induced atomic and energy currents in response to perturbations with an external potential. We induce currents through two distinct experimental protocols; by applying a constant force to the gas, and by joining two subsystems prepared in different equilibrium states. By virtue of integrability, dynamics of the system is governed by ballistically propagating, long-lived quasi-particle excitations, whereby Drude weights almost fully characterise large-scale transport. Indeed, our results align with predictions from a recently developed hydrodynamic theory, demonstrating almost fully dissipationless transport, even at finite temperatures and interactions. These findings not only provide experimental validation of the hydrodynamic predictions but also offer methodologies applicable to various condensed matter systems, facilitating further studies on the transport properties of strongly correlated quantum matter.

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

0 major / 3 minor

Summary. The manuscript measures Drude weights in a one-dimensional ultracold Bose gas of interacting atoms using two protocols (constant external force and joining of subsystems prepared at different equilibria). By virtue of integrability of the Lieb-Liniger model, the dynamics are governed by long-lived ballistic quasiparticles; the extracted Drude weights are shown to align quantitatively with a recently developed hydrodynamic theory, indicating that transport remains almost fully dissipationless (negligible regular conductivity) at the accessed finite temperatures and interaction strengths. Currents are reported to remain constant over the longest experimentally accessible times in both protocols.

Significance. If the quantitative alignment and absence of detectable decay hold, the work supplies direct experimental validation of hydrodynamic predictions for Drude weights in the Lieb-Liniger gas together with reproducible protocols that can be transferred to other integrable or near-integrable condensed-matter systems. The dual-protocol consistency and explicit comparison to parameter-free hydrodynamic formulas constitute a clear strength.

minor comments (3)
  1. [§3] §3 (or wherever the hydrodynamic formulas are introduced): the text should explicitly state the range of temperatures and interaction parameters (e.g., values of γ and T/E_F) over which the comparison is performed and confirm that the regular part of the conductivity remains below the experimental resolution.
  2. [Methods/Figures] Figure captions and methods section: include a brief statement of how the current is extracted from density profiles (e.g., fitting procedure, integration window) and report the longest evolution time used to establish the absence of decay.
  3. Notation: ensure consistent use of D (Drude weight) versus D_n or D_e for particle versus energy currents throughout the text and equations.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for their positive assessment of our work, including the recognition of the quantitative agreement with hydrodynamic theory and the reproducibility of the protocols. The recommendation for minor revision is noted. No specific major comments appear in the report, so we provide no point-by-point rebuttals below. We will incorporate any minor suggestions during revision.

Circularity Check

0 steps flagged

No significant circularity; derivation relies on external hydrodynamic theory

full rationale

The paper reports experimental measurements of Drude weights via two protocols in an integrable 1D Bose gas and compares the extracted values to independent predictions from a recently developed hydrodynamic theory. The central claim—that Drude weights almost fully characterize transport due to integrability—is justified by reference to that external theory rather than by any internal fit, self-definition, or self-citation chain. No equation or result reduces by construction to its own inputs; the alignment is presented as validation against an outside benchmark. This is the most common honest outcome for an experimental paper whose load-bearing step is comparison to independently derived formulas.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Abstract-only review prevents exhaustive extraction; the central claim rests on the domain assumption of integrability and the applicability of the cited hydrodynamic theory.

axioms (1)
  • domain assumption Dynamics of the system is governed by ballistically propagating, long-lived quasi-particle excitations due to integrability
    Invoked in the abstract to justify that Drude weights almost fully characterise large-scale transport.

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Forward citations

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Reference graph

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