近日，瑞士苏黎世联邦理工学院的Tilman Esslinger&Meng-Zi Huang及其研究团队取得一项新进展。经过不懈努力，他们对由费米子超流动性增强的不可逆熵输运过程进行研究。相关研究成果已于2024年4月22日在国际知名学术期刊《自然—物理学》上发表。
该研究团队观察到，当粒子和熵通过连接两个强相互作用费米子超流体的弹道通道流动时，它们呈现出显著的大并发流动现象。这两种电流对化学势和温度偏差的反应均呈现出非线性特征。研究人员发现，在线性状态下，每个粒子传递的熵量远超超流体力学的预测，并且这一现象在很大程度上并不受通道几何形状变化的影响。
相较之下，对流和扩散熵输运的时间尺度则随着通道几何形状的变化而表现出显著差异。在此研究设置中，超流动性的存在反而提升了熵传递的速度。此外，研究人员还成功构建了一个现象学模型，用于描述广义梯度动力学框架内的非线性动力学过程。
该研究中测量熵流的方法可能有助于阐明超流体和超导装置中的传热机制。
据悉，两种超流体之间的粒子和熵流动特性，通常被视为由无熵的宏观波函数所驱动的可逆流动过程。尽管这个波函数赋予了超流体和超导体众多引人入胜的特性，但它在非平衡状态下与激励之间如何相互作用，至今尚不清楚。
附：英文原文
Title: Irreversible entropy transport enhanced by fermionic superfluidity
Author: Fabritius, Philipp, Mohan, Jeffrey, Talebi, Mohsen, Wili, Simon, Zwerger, Wilhelm, Huang, Meng-Zi, Esslinger, Tilman
Issue&Volume: 2024-04-22
Abstract: The nature of particle and entropy flow between two superfluids is often understood in terms of reversible flow carried by an entropy-free, macroscopic wavefunction. While this wavefunction is responsible for many intriguing properties of superfluids and superconductors, its interplay with excitations in non-equilibrium situations is less understood. Here we observe large concurrent flows of both particles and entropy through a ballistic channel connecting two strongly interacting fermionic superfluids. Both currents respond nonlinearly to chemical potential and temperature biases. We find that the entropy transported per particle is much larger than the prediction of superfluid hydrodynamics in the linear regime and largely independent of changes in the channel’s geometry. By contrast, the timescales of advective and diffusive entropy transport vary significantly with the channel geometry. In our setting, superfluidity counterintuitively increases the speed of entropy transport. Moreover, we develop a phenomenological model describing the nonlinear dynamics within the framework of generalized gradient dynamics. Our approach for measuring entropy currents may help elucidate mechanisms of heat transfer in superfluids and superconducting devices.
DOI: 10.1038/s41567-024-02483-3
Source: https://www.nature.com/articles/s41567-024-02483-3