Quantum fluctuation-driven transport crossover between two liquid states in distinguishable helium-4

Mika Tanabe; Momoko Tsujimoto; Kenichi Kinugawa

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arXiv · 2607.23127

Quantum fluctuation-driven transport crossover between two liquid states in distinguishable helium-4

Mika Tanabe·Momoko Tsujimoto·Kenichi Kinugawa

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Abstract

We show the emergence of a quantum fluctuation-driven transport crossover between two liquid states in distinguishable helium-4 obeying Boltzmann statistics, in the absence of atomic exchange. Using path integral centroid molecular dynamics simulations over 0.1-3.3 K and 1-60 bar, we investigate the transport properties of two distinct liquid states: the low quantum-dispersion liquid (LQDL) and the high quantum-dispersion liquid (HQDL). While LQDL exhibits conventional liquid behavior consistent with the Stokes-Einstein (SE) relation, HQDL emerges at lower temperatures and displays anomalous gas-like transport characterized by superdiffusion and ultralow viscosity, accompanied by a breakdown of the SE relation. This counterintuitive emergence of gas-like dynamics upon cooling reflects the dominant role of nuclear quantum fluctuations, in contrast to thermal fluctuations at higher temperatures. Across the LQDL-HQDL boundary, we identify a transport crossover marked by a qualitative change in the velocity autocorrelation function (VAF), a transition in the Prandtl number, and the emergence of transport minima in shear and kinematic viscosities, thermal conductivity, and thermal diffusivity. These minima reflect a crossover from liquid-like to gas-like transport upon cooling in the low-temperature subcritical region, in addition to the universal transport minima observed in the supercritical regime. The transition from oscillatory to monotonic VAF defines a second Frenkel line, distinct from the conventional Frenkel line observed in the supercritical region. LQDL is a heat-transport-dominated dissipative fluid, whereas HQDL is a momentum-dominated inertial fluid. These results demonstrate that nuclear quantum fluctuations alone induce gas-like liquid behavior and provide a unified picture of transport phenomena in distinguishable helium-4 without superfluidity.

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cond-mat.stat-mech cond-mat.dis-nn cond-mat.mtrl-sci cond-mat.quant-gas quant-ph

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Mika Tanabe, Momoko Tsujimoto, Kenichi Kinugawa. 2026-07-25. Quantum fluctuation-driven transport crossover between two liquid states in distinguishable helium-4. https://arxiv.org/abs/2607.23127

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