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

美国国家科学基金会和美国--以色列双国科学基金会(BSF)共同支持美国和以色列研究人员之间的这一合作。美国国家科学基金会材料研究部资助了这一奖项，该奖项支持金属系统中电荷和热传输的基本方面的研究和教育。对流经凝聚态物质系统的电流的测量通常是描述新合成材料的特征或对有趣的物质相的性质进行更深入了解的首选工具。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动的情况下，也可以驱动热流。虽然在许多系统中已经对电传输进行了广泛的研究，但对热或热电传输的了解仍然相对较少。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理解是至关重要的。这就是本研究项目的主要目的。除了它的科学价值，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研究员。具体地说，初级参与者可以从这种国际合作中受益匪浅，这将使他们能够在著名的非美国研究所进行长期访问，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。TECHNICAL SUMMARY美国国家科学基金会和美国-以色列双国科学基金会(BSF)共同支持美国和以色列研究人员之间的这种合作。美国国家科学基金会材料研究部资助这一奖项，该奖项支持相关电子系统中热和热电传输的研究和教育。在相关的电子系统中，热输运系数和热电输运系数在探测电子动力学的不同方面时提供了补充信息。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的输运过程的理论理解是至关重要的。复杂材料输运的理论理解常常受到多种因素的阻碍，包括强关联、杂质、费米表面几何和声子。因此，重要的是研究只出现其中一些复杂情况的系统，并且可以孤立地研究这些系统，以获得可能随后应用于更复杂系统的见解。遵循这一策略，研究将首先集中在金属-绝缘体相变附近的无序电子液体，然后扩展到更多奇异的强关联系统。研究项目的主要目标是：(I)从理论上研究无序电子液体中金属-绝缘体相变金属侧的热电势的温度依赖关系。特别是，我们将探索可能违反Mott关系的情况以及粒子-空穴不对称的作用。(2)探讨强相互作用对电和热传输的影响。在二维电子液体中，我们打算探索由杂质散射主导的低温区域和电子-电子碰撞占优势的较高温度之间的交叉处的电子输运。对于强关联的材料，该项目将专注于对不均匀温度的响应，在不均匀的温度下，类似的机制可能会发挥作用。加深我们对热电和热传输的基本机制的了解，特别是在半导体中，可能会提高电子设备的能效。特别是，热电制冷器和发电机可以受益于了解材料属性，如无序、相互作用或到临界点的距离如何影响传输系数。这项活动的进一步影响将在于培养研究生和博士后研究员。具体地说，初级参与者可以从这一国际合作中受益匪浅，这将使他们能够在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NSF的法定使命，并通过使用基金会的智力优势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.