可区分氦 - 4 中量子涨落驱动的两种液态之间的输运转变
Quantum fluctuation-driven transport crossover between two liquid states in distinguishable helium-4
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中文总结 AI 辅助
研究可区分氦 - 4 中两种液态的输运，通过路径积分质心分子动力学模拟，发现核量子涨落驱动输运转变，低温度下出现高量子色散液体，有超扩散等反常气体状输运特征，给出该体系输运现象统一图景。
中文摘要 AI 辅助
我们展示了在服从玻尔兹曼统计且不存在原子交换的可区分氦 - 4 中，量子涨落驱动的两种液态之间的输运转变。通过在 0.1 - 3.3K 和 1 - 60 巴下的路径积分质心分子动力学模拟，研究了两种不同液态的输运性质：低量子色散液体（LQDL）和高量子色散液体（HQDL）。LQDL 表现出符合斯托克斯 - 爱因斯坦（SE）关系的传统液体行为，HQDL 在较低温度出现，具有超扩散和超低粘度等反常气体状输运特征，且 SE 关系失效。冷却时这种反常的气体状动力学出现反映了核量子涨落的主导作用。跨越 LQDL - HQDL 边界，有输运转变，表现为速度自相关函数的定性变化、普朗特数的转变以及剪切和运动粘度、热导率和热扩散率中输运最小值的出现。LQDL 是热输运主导的耗散流体而 HQDL 是动量主导的惯性流体。这些结果表明仅核量子涨落就能诱导气体状液体行为，并提供了无超流性的可区分氦 - 4 中输运现象的统一图景。
英文摘要
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.
