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中国物理学会期刊

一维p波费米气体的输运性质

Transport Properties in One-dimensional p-wave Fermi Gases

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  • 非遍历动力学中的输运是量子多体物理的重要课题, 可积系统凭借其无穷多守恒量展现出独特的弹道输运特性. 基于 Bethe ansatz 与广义流体动力学理论, 系统地研究了一维吸引相互作用 p波费米气体的平衡与非平衡输运性质. 在热力学 Bethe ansatz 方程和广义流体动力学框架下给出了描述弹道输运的 Drude weight 表达式, 并建立了其与基本热力学量 (例如粒子数密度、能量密度和熵等) 之间的普适关系. 通过解析推导与数值模拟, 给出了 Drude weight 在低温和有限温度下在弱相互作用区域的演化规律, 以及在量子临界区所遵循的普适标度行为. 在非平衡输运方面, 阐述了倾斜势、局域化学势差与局域温度差三种情况下的输运过程, 还分析了粒子流和能量流的演化, 验证了理论框架的自洽性. 本研究不仅为理解一维 p 波费米气体的弹道输运提供了系统的理论框架, 有利于加深对一维量子连续可积系统输运性质的理解.

     

    Transport in nonergodic dynamics is a fundamental topic in quantum many-body physics. Integrable systems, due to their infinite number of conserved quantities, exhibit unique ballistic transport properties. In this work, we systematically investigate an integrable model of cold atomic gases—the one-dimensional p-wave Fermi gas. Although the theoretical description of this model has been extensively studied, its ballistic transport properties have not yet been fully elucidated. Within the framework of thermodynamic Bethe ansatz (TBA) equations and Generalized Hydrodynamics (GHD), we derive an expression for the Drude weight that characterizes ballistic transport and establish a universal relation linking it to basic thermodynamic quantities such as particle density, energy density, and entropy. This relation holds in all integrable systems satisfying Galilean invariance. Under equilibrium conditions and for weak interactions, we obtain the low-temperature thermodynamic quantities and the Drude weight via Sommerfeld expansion, and further explore the dependence of the Drude weight on both interaction strength and temperature. For non-equilibrium states, we analyze the evolution under three protocols—tilted potential, local chemical potential difference, and local temperature difference—all governed by the GHD equations. Numerical calculations of the transport coeffcients in steady states agree perfectly with the results obtained from integral expressions, further validating the reliability of the theoretical framework. Furthermore, using the polylogarithm function, we derive a universal scaling equation for the transport coeffcients. It is found that the transport coeffcients exhibit clear scaling behavior near the quantum critical point of the transition from the vacuum state to a finite-density Fermi state, and their temperature dependence is consistent with the universality class characterized by dynamical exponent z = 2 and correlation length exponent ν = 1/2, thereby confirming the self-consistency of the theory. This work not only provides a systematic theoretical framework for understanding ballistic transport in one-dimensional p-wave Fermi gases but also deepens the general understanding of transport properties in one-dimensional quantum continuum integrable systems.

     

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