Transport and Nonequilibrium Effects in Strongly Correlated Multilayer Nanostructure

该奖项支持与处理由强相关多层组成的多层器件中的输运和非线性效应有关的理论和计算研究以及教育活动。新的形式和计算算法将被开发出来，然后应用到世界各地领先的实验小组正在实验研究的系统中。特别是，工作包括：(i)开发了一种新的数值重整化群计算方法，该方法消除了特别展宽，能够准确地处理高能量和低能尺度，从而能够计算绝缘体和费米液体中的直流输运。（ii）发展基于格林函数的密度泛函理论方法，用于确定多层系统的热电特性。当热电材料被纳入旨在阻止声子传输的多层结构中时，这项技术将用于制定如何维持（或增加）塞贝克效应的设计规则。（iii）发展了一种精确的非平衡动态平均场理论方法，以确定由电流偏态Falicov-Kimball模型描述的多层器件的电流-电压特性。对于非平衡杂质问题（类似于连续时间量子蒙特卡罗方法的杂化展开），在强耦合和大驱动场下处理Hubbard和周期性Anderson模型的基于强耦合的方法也将进行研究。（iv）研究用强相关材料代替介电层或金属板的平行板电容器的电容的强相关效应。这项理论和计算工作将与实验工作相协调，包括德国的Jochen Mannhart（电容器），日本的Yuji Matsuda（重费米子多层中的电荷和热传输）和美国莱斯大学的Doug Natelson（接触和大部分强相关材料中的开关效应）的实验工作。该项目支持在学术研究环境和IBM阿尔马登研究中心为期一年的研究实习中培养计算物理学研究生。该项目还为本科生提供研究经验，他们将通过在克罗地亚萨格勒布物理研究所的暑期实习了解国际科学合作。通过参与乔治城大学公共利益科学项目的暑期项目，本科生也将有机会更深入地了解科学和科学家在整个社会中的作用。该奖项支持与电荷和热传输处理相关的理论和计算研究以及教育活动，这些传输是由多层电子相互作用导致高度相关的运动组成的。这些材料对环境有很大的敏感性，这使得它们适合用于所谓的智能材料设备，可以改善许多不同电子设备的工作方式。新的形式和计算算法将被开发出来，然后应用到世界各地领先的实验小组正在实验研究的系统中。一些例子包括：(i)检查如何在这些系统中修改电容（存储电荷的能力），（ii）检查热感应电流或电流感应热传输在这种尺寸比人类头发小10万倍的多层系统中，（iii）通过研究所谓的非线性效应，研究这些器件如何违反欧姆定律（欧姆定律指出电阻上的电压降与通过电阻的电流成线性比例），这可能会导致超高速电子开关。该项目支持在学术研究环境和IBM阿尔马登研究中心为期一年的研究实习中培养计算物理学研究生。该项目还为本科生提供研究经验，他们将通过在克罗地亚萨格勒布物理研究所的暑期实习了解国际科学合作。通过参与乔治城大学公共利益科学项目的暑期项目，本科生也将有机会更深入地了解科学和科学家在整个社会中的作用。

TECHNICAL SUMMARYThis award supports theoretical and computational research and educational activities related to the treatment of transport and nonlinear effects in multilayered devices composed of strongly correlated multilayers. New formalisms and computational algorithms will be developed and then applied to systems that are being investigated experimentally by leading experimental groups around the world.In particular, the work includes:(i) Development of a new method for numerical renormalization group calculations that removes the ad hoc broadening and is able to accurately treat both high and low energy scales, enabling calculation of dc transport in both insulators and Fermi liquids. (ii) Development of a Green's function based density functional theory approach for determining thermoelectric properties of multilayered systems. This technique will be used to formulate design rules for how to maintain (or increase) the Seebeck effect when thermoelectric materials are incorporated into multilayer structures designed to block phonon transport.(iii) Development of an exact non-equilibrium dynamical mean-field theory approach to determine the current-voltage characteristic of a multilayered device described by a current biased Falicov-Kimball model. A strong-coupling based approach for the non-equilibrium impurity problem (similar to a hybridization expansion for continuous time quantum Monte Carlo approaches) to treat Hubbard and periodic Anderson models at strong coupling and with large driving fields will also be examined.(iv) Investigation of strong correlation effects on the capacitance of a parallel plate capacitor in which the dielectric layers or the metallic plates are replaced by strongly correlated materials. This theoretical and computational work will be coordinated with experimental efforts, including those of Jochen Mannhart in Germany (capacitors), Yuji Matsuda in Japan (charge and heat transport in heavy fermion multilayers), and Doug Natelson at Rice University, US (switching effects in contacts and in the bulk of strongly correlated materials).This project supports the training of graduate students in computational physics, both in the academic research environment and through year-long research internships at the IBM Almaden Research Center. The project also provides research experiences for undergraduate students, who will learn about international collaboration in science through summer internships at the Institute for Physics in Zagreb, Croatia. By engaging in a summer project with Georgetown's Program on Science in the Public Interest, undergraduates will also have the opportunity to gain a deeper understanding of the role of science and scientists in society at large.NONTECHNICAL SUMMARYThis award supports theoretical and computational research and educational activities related to the treatment of charge and heat transport in devices composed of several layers in which electrons interact strongly with each other leading to highly correlated motion. These materials have a large sensitivity to their environment, which makes them suitable for use in so-called smart-material devices which can improve the way many different electronic devices work. New formalisms and computational algorithms will be developed and then applied to systems that are being investigated experimentally by leading experimental groups around the world. Some examples include (i) examining how capacitance (capacity to store charge) can be modified in these systems, (ii) examining heat-induced electrical current or electrical current-induced heat transport in such multi-layer systems of sizes some 100,000 times smaller than the human hair, and (iii) examining how Ohm's law (which states that the voltage drop across a resistor is linearly proportional to the current through it) is violated in these devices by studying the so-called non-linear effects, that could potentially lead to ultrafast electronic switches. This project supports the training of graduate students in computational physics, both in the academic research environment and through year-long research internships at the IBM Almaden Research Center. The project also provides research experiences for undergraduate students, who will learn about international collaboration in science through summer internships at the Institute for Physics in Zagreb, Croatia. By engaging in a summer project with Georgetown's Program on Science in the Public Interest, undergraduates will also have the opportunity to gain a deeper understanding of the role of science and scientists in society at large.