Materials Department, University of California, Santa Barbara, CA 93106-5050, United States of America.
Rep Prog Phys. 2018 Jun;81(6):062502. doi: 10.1088/1361-6633/aabdfa. Epub 2018 Apr 13.
Understanding the anomalous transport properties of strongly correlated materials is one of the most formidable challenges in condensed matter physics. For example, one encounters metal-insulator transitions, deviations from Landau Fermi liquid behavior, longitudinal and Hall scattering rate separation, a pseudogap phase, and bad metal behavior. These properties have been studied extensively in bulk materials, such as the unconventional superconductors and heavy fermion systems. Oxide heterostructures have recently emerged as new platforms to probe, control, and understand strong correlation phenomena. This article focuses on unconventional transport phenomena in oxide thin film systems. We use specific systems as examples, namely charge carriers in SrTiO layers and interfaces with SrTiO, and strained rare earth nickelate thin films. While doped SrTiO layers appear to be a well behaved, though complex, electron gas or Fermi liquid, the rare earth nickelates are a highly correlated electron system that may be classified as a non-Fermi liquid. We discuss insights into the underlying physics that can be gained from studying the emergence of non-Fermi liquid behavior as a function of the heterostructure parameters. We also discuss the role of lattice symmetry and disorder in phenomena such as metal-insulator transitions in strongly correlated heterostructures.
理解强关联材料的异常输运性质是凝聚态物理中最具挑战性的问题之一。例如，人们遇到金属-绝缘体转变、偏离朗道费米液体行为、纵向和 Hall 散射率分离、赝能隙相和不良金属行为。这些性质在块状材料中得到了广泛的研究，如非常规超导体和重费米子系统。氧化物异质结构最近成为了探测、控制和理解强关联现象的新平台。本文重点介绍了氧化物薄膜系统中的非常规输运现象。我们使用特定的系统作为例子，即 SrTiO 层中的电荷载流子和与 SrTiO 的界面，以及应变的稀土镍酸盐薄膜。虽然掺杂 SrTiO 层似乎是一个表现良好、尽管复杂的电子气或费米液体，但稀土镍酸盐是一个高度关联的电子系统，可能被归类为非费米液体。我们讨论了从研究非费米液体行为的出现作为异质结构参数的函数中获得的基础物理的见解。我们还讨论了晶格对称性和无序在强关联异质结构中的金属-绝缘体转变等现象中的作用。
