么正费米气体中Wiedemann-Franz定律的破缺
Breakdown of the Wiedemann-Franz law in a unitary Fermi gas
摘要：
我们报告耦合的热量和粒子传输测量通过量子点接触（QPC）连接两个水库的共振相互作用，有限温度费米气体。在加热其中一个之后，我们观察到粒子电流从冷到热流动。我们监测的温度演变的水库，并发现该系统的演变后，初始响应到一个非平衡的稳态与有限的温度和化学电势差在QPC。在这种状态下，以热和粒子流形式出现的任何弛豫都消失了。从我们的测量中，我们提取的QPC的传输系数，并推导出违反Wiedemann-Franz定律的一个数量级的洛伦兹数，一个特性持续甚至广泛的接触。与此相反，塞贝克系数采取的值接近于预期的非相互作用的费米气体，并显示出平稳的减少，原子密度接近QPC增加超过超流过渡。我们的工作代表了超流氦观测到的喷泉效应的费米模拟，并对酉费米气体有限温度动力学的微观建模提出了新的挑战。
英文摘要：
We report on coupled heat and particle transport measurements through a quantum point contact (QPC) connecting two reservoirs of resonantly interacting, finite temperature Fermi gases. After heating one of them, we observe a particle current flowing from cold to hot. We monitor the temperature evolution of the reservoirs and find that the system evolves after an initial response into a non-equilibrium steady state with finite temperature and chemical potential differences across the QPC. In this state any relaxation in the form of heat and particle currents vanishes. From our measurements we extract the transport coefficients of the QPC and deduce a Lorenz number violating the Wiedemann-Franz law by one order of magnitude, a characteristic persisting even for a wide contact. In contrast, the Seebeck coefficient takes a value close to that expected for a non-interacting Fermi gas and shows a smooth decrease as the atom density close to the QPC is increased beyond the superfluid transition. Our work represents a fermionic analog of the fountain effect observed with superfluid helium and poses new challenges for microscopic modeling of the finite temperature dynamics of the unitary Fermi gas.
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