NSF/DMR-BSF: Quantum transport of charge and heat in correlated electron systems

美国国家科学基金会和美以两国国家科学基金会（BSF）共同支持美国和以色列研究人员之间的合作。该奖项由美国国家科学基金会材料研究部门资助，旨在支持金属系统中电荷和热输运基本方面的研究和教育。测量通过凝聚态系统的电流通常是表征新合成材料的首选工具，或者是对物质有趣相的本质有更深入的了解。通常，测量热流可以提供有价值的补充信息，特别是在量子力学效应和载流子之间的相互作用很重要的情况下。这是因为即使在电荷载体不移动的情况下，热流也能被驱动。虽然电输运在许多系统中得到了广泛的研究，但热输运或热电输运仍然相对知之甚少。因此，为了充分利用现有的实验技术，进一步提高我们对这些传输过程的理论认识是至关重要的。这就是这个研究项目的主要目标。除了其科学价值之外，更好地了解电荷和热传输的基本机制，特别是在半导体中，有望提高电子设备的能源效率。这项活动的进一步影响将在于培养研究生和博士后。具体来说，初级参与者可以从这种国际合作中受益匪浅，这将使他们能够在一个著名的非美国机构进行长期访问，在那里他们可以接触到不同的想法和方法，并建立有助于他们未来职业生涯的联系。美国国家科学基金会和美以两国国家科学基金会（BSF）共同支持美国和以色列研究人员之间的合作。该奖项由美国国家科学基金会材料研究部门资助，用于支持相关电子系统中热电输运的研究和教育。在相关电子系统中，热和热电输运系数提供了互补的信息，因为它们探测了电子动力学的不同方面。为了充分利用这些实验技术，进一步提高我们对涉及电荷和热量的输运过程的理论认识是至关重要的。复杂材料中输运的理论认识经常受到多种因素的阻碍，包括强相关性、杂质、费米表面几何形状和声子。因此，重要的是要研究只发生其中一些复杂情况的系统，并且可以单独研究，以获得可能应用于更复杂系统的见解。按照这一策略，研究将首先集中在金属-绝缘体跃迁附近的无序电子液体上，然后扩展到包括更奇特的强相关系统。本课题的主要目标是：(1)从理论上研究无序电子液体中金属-绝缘体跃迁的金属侧热功率对温度的依赖关系。特别是，我们将探索可能违反莫特关系和粒子-空穴不对称的作用。（ii）探讨强相互作用对电和热输运的影响。在二维电子液体中，我们打算探索以杂质散射为主的低温区和以电子-电子碰撞为主的高温区之间的交叉区的电输运。对于强相关材料，该项目将重点关注对非均匀温度的响应，在那里类似的机制可以起作用。加深我们对热电和热输运的基本机制的了解，特别是在半导体中，可以提高电子设备的能源效率。特别是，热电冷却器和发电机可以从了解材料性质（如无序性、相互作用或与临界点的距离）如何影响传输系数中受益。这项活动的进一步影响将在于培养研究生和博士后。具体来说，初级参与者可以从这种国际合作中受益匪浅，这将使他们能够在一个著名的非美国机构进行长期访问，在那里他们可以接触到不同的想法和方法，并建立有助于他们未来职业生涯的联系。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NONTECHNICAL SUMMARYThe National Science Foundation and the United States -- Israel Binational Science Foundation (BSF) jointly support this collaboration between a US- and an Israel-based researcher. The NSF Division of Materials Research funds this award, which supports research and education on fundamental aspects of charge and heat transport in metallic systems. Measurements of electric currents that flow through a condensed matter system are often the tool of first resort for characterizing newly synthesized materials, or for gaininig deeper insights into the nature of interesting phases of matter. Often, measuring the flow of heat can provide valuable supplementary information, in particular in cases where quantum mechanical effects and interactions between the carriers are important. This is because heat currents can be driven even when electric charge carriers are immobile. While electric transport has been studied extensively in many systems, thermal or thermoelectric transport remains relatively poorly understood. To take full advantage of existing experimental techniques, it is therefore crucial to further improve our theoretical understanding of these transport processes. That is the main goal of this research project. In additional to its scientific merit, better knowledge of fundamental mechanisms of charge and heat transport, especially in semiconductors, holds promise for improving energy efficiency in electronic devices. Further impact of this activity will lie in training graduate students and postdoctoral fellows. Specifically, junior participants can greatly benefit from this international collaboration, which will allow them extended visits at a prestigious, non-US institute where they can be exposed to different ideas and approaches, and make connections that will help them in their future careers.TECHNICAL SUMMARYThe National Science Foundation and the United States -- Israel Binational Science Foundation (BSF) jointly support this collaboration between a US- and an Israel-based researcher. The NSF Division of Materials Research funds this award, which supports research and education on thermal and thermoelectric transport in correlated electron systems. In correlated electron systems, thermal and thermoelectric transport coefficients offer complementary information as they probe different aspects of the electron dynamics. To take full advantage of these experimental techniques, it is crucial to further improve our theoretical understanding of transport processes involving both electric charge and heat. Theoretical understanding of transport in complex materials is often impeded by multiple factors including strong correlations, impurities, Fermi-surface geometry, and phonons. It is therefore important to study systems where only some of these complications occur and can be studied in isolation to gain insights that may then be applied to more complex systems. Following this strategy, the research will initially focus on the disordered electron liquid near the metal-insulator transition, and then branch out to include more exotic strongly correlated systems.The main goals of the research project are: (i) To study theoretically the temperature dependence of the thermopower on the metallic side of the metal-insulator transition in disordered electron liquids. In particular, we will explore possible violations of the Mott-relation and the role of particle-hole asymmetry. (ii) To explore the effects of strong interactions on electric and thermal transport. In two-dimensional electron liquids, we intend to explore electric transport at the crossover between the low-temperature regime dominated by impurity scattering and higher temperatures where electron-electron collisions prevail. For strongly correlated materials, the project will focus on the response to a nonuniform temperature, where similar mechanisms can be at work.Deepening our knowledge on fundamental mechanisms of thermoelectric and thermal transport, especially in semiconductors, may improve energy efficiency in electronic devices. In particular, thermoelectric coolers and generators could benefit from understanding how material properties like disorder, interactions or the distance from a critical point affect transport coefficients. Further impact of this activity will lie in training graduate students and postdoctoral fellows. Specifically, junior participants can greatly benefit from this international collaboration, which will allow them extended visits at a prestigious, non-US institute where they can be exposed to different ideas and approaches, and make connections that will help them in their future careers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.