标题： 粒子-空穴对称系统中的流体力学：量子蒙特卡洛研究 显示英文标题

标题： Hydrodynamics of particle-hole symmetric systems: a quantum Monte Carlo study

摘要： 在洁净且具有粒子-空穴对称性的系统中半满时电子流中出现的流体力学行为是一个非平凡的问题。Navier-Stokes（NS）方程描述了动量流，而实验测量通常捕捉电流流型。然而，在粒子-空穴对称系统中，电荷电流和动量流完全解耦，因为电子和空穴以相反方向运动且分布函数相同。这使得将NS方程与观测到的流型联系起来变得困难。在这项工作中，我们证明了即使没有动量流，电荷电流的流体力学行为也可以出现。通过结合玻尔兹曼输运理论与数值精确的清洁石墨烯样本的量子蒙特卡洛模拟，我们表明可以直接从NS型方程导出电荷电流，无需任何额外机制来耦合速度场和电荷电流以解释半满石墨烯中观测到的流体力学流型。我们发现一个新的输运量——电流扩散系数——取代粘度，并期望这种描述适用于任何粒子-空穴对称系统。我们的结果为实验数据的解释提供了新的见解，并展示了量子蒙特卡洛计算如何作为实验的替代方法在输运测量中验证动力学理论的结果。 显示英文摘要

摘要： The emergence of hydrodynamic behavior in electronic flow within clean, particle-hole-symmetric systems at half-filling is a non-trivial problem. Navier-Stokes (NS) equations describe the momentum flow, while experimental measurements typically capture the current flow profiles. However, in particle-hole-symmetric systems, electric current and momentum flow are entirely decoupled because electrons and holes move in opposite directions with equal distribution functions. This makes it challenging to link NS equations to observed flow patterns. In this work, we demonstrate that the hydrodynamic behavior of the charge current at half filling can emerge despite the absence of momentum flow. By combining Boltzmann transport theory with numerically exact Quantum Monte Carlo simulations of clean graphene samples, we show that NS-type equations can be derived directly for the charge current, eliminating the need for any additional mechanism coupling the velocity field and charge current in explaining the experimentally observed hydrodynamic flow profiles in graphene at half-filling. We show that a new transport quantity - the current diffusion coefficient - replaces viscosity and expect this description to be valid for any particle-hole symmetric system. Our results provide new insights into the interpretation of experimental data and demonstrate how Quantum Monte Carlo calculations can serve as an alternative to experiments in transport measurements to verify the kinetic theory results.