Department of Physics, Harvard University, Cambridge, MA 02138, USA. John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
Department of Physics, Harvard University, Cambridge, MA 02138, USA.
Science. 2016 Mar 4;351(6277):1058-61. doi: 10.1126/science.aad0343. Epub 2016 Feb 11.
Interactions between particles in quantum many-body systems can lead to collective behavior described by hydrodynamics. One such system is the electron-hole plasma in graphene near the charge-neutrality point, which can form a strongly coupled Dirac fluid. This charge-neutral plasma of quasi-relativistic fermions is expected to exhibit a substantial enhancement of the thermal conductivity, thanks to decoupling of charge and heat currents within hydrodynamics. Employing high-sensitivity Johnson noise thermometry, we report an order of magnitude increase in the thermal conductivity and the breakdown of the Wiedemann-Franz law in the thermally populated charge-neutral plasma in graphene. This result is a signature of the Dirac fluid and constitutes direct evidence of collective motion in a quantum electronic fluid.
量子多体系统中的粒子相互作用可以导致由流体力学描述的集体行为。这样的系统之一是在电荷中性点附近的石墨烯中的电子-空穴等离子体，它可以形成强耦合的狄拉克流体。由于在流体力学中电荷和热流的解耦，这种准相对论费米子的电荷中性等离子体有望表现出热导率的实质性增强。利用高灵敏度的约翰逊噪声测温法，我们在石墨烯中的热平衡电荷中性等离子体中报告了热导率的一个数量级的增加和魏德曼-弗朗茨定律的破坏。这一结果是狄拉克流体的特征，也是量子电子流体中集体运动的直接证据。
