- Cerfe Labs articles. CeRAM technology developed by Cerfe Labs uses correlated electron physics, which might be new for most of our readers. To address this, we have written three articles to provide a starter kit for the general audience, engineers, and semiconductors professionals. Our first article introduces semiconductors and memory. In the second article, we provide a basic understanding of CeRAM technology. We have also provided an introduction for semiconductor professionals.
Through this article series, we hope to provide a good foundation for beginners as well as professionals and prepare them for the exciting world of correlated electron physics that can be further explored through the curated list of publications, articles, lecture notes, and books described below
- Review papers. “Metal-insulator transitions” is a seminal review paper by Imada, Fujimori, and Tokura that does a great job in summarization observations and current understanding of the metal-insulator transitions with an extremely thorough history.
The paper “Mott Memory and Neuromorphic Devices” by You Zhou and Shriram Ramanathan discuss the implications of Mott transition in semiconductor memory and information processing. The primary device discussed here is a metal-insulator-metal sandwich similar to the CeRAM device. The same authors also provide a review of three-terminal field-effect transistor kind of device made from correlated electron materials in the paper “Correlated Electron Materials and Field-Effect Transistors for Logic: A Review”.
Correlated electrons have applications beyond memories and logic devices. As discussed in the introductory section, these materials can be used for optical sensors, metamaterials, thermal switches, and many other applications. Such a wide variety of reviews is captured in “Oxide Electronics Utilizing Ultrafast Metal-Insulator Transitions” by Yang, Ko, and Ramanathan from Harvard University.
The paper “Opportunities in Vanadium-based Strongly Correlated Electron Systems” discusses the physical framework and basic properties of the Vanadium compound and practical applications that can potentially augment existing technologies.
- Popular science. Prof. Yoshinori Tokura has been a strong proponent of correlated electron materials. You can read his interview in Dreams of New Technologies for a Sustainable Society. Two articles worth mention is A brief introduction to strongly correlated electronic materials and Correlated Electrons.
- History of Mott and Mott insulators. Neville Francis Mott has contributed significantly to the field of condensed matter physics. You can find the list of all of his publications here or read his selected papers here. Among these many seminal works, his first paper alluding to the significance of transition metals and collective electron behavior was published in 1949. In the paper “The Basis of the Electron Theory of Metals, with Special Reference to the Transition Metals” Mott specifically discusses the role of partially filled orbitals and electron correlation that makes NiO insulating. In 1958, Mott further solidified his theory and showed that the Block wave function-based band theory of solids is not universal. In the lecture, “The transition from the Metallic to the Non-Metallic State” Mott argued that electronic Colombic force is essential in determining the state of the metal.
- Lecture and course notes. If you are completely new to the field of Mott insulators, there is Quick and Dirty Introduction to Mott Insulators by Prof. Branislav Nikolic from the University of Delaware.
- Books. In the boom “Multifunctional Oxide Heterostructures”, Dagotto and Tokura provide A brief introduction to strongly correlated electronic materials. We believe that this chapter might be more advanced than CeRAM physics presented here, it is worth reading if you want an introduction to the cutting-edge work done in the field.
The study of correlated electron physics requires modern mathematical tools. We believe that a starting book for graduate-level courses is Condensed Matter Field Theory by Atland and Simons. This book develops mathematical formalism required to solve the multi-particle problem such as electron correlation and also applies the formalism to concrete problems.
- Physics of correlated electron materials. Efros and Shklovskii discuss the Critical Behaviour of Conductivity and Dielectric Constant near the Metal-Non-Metal Transition Threshold.
The doping of correlated electron materials remains a mystery. Researchers have recently attempted to solve the doping theory of mott insulators in the work “Exact theory of superconductivity in a doped Mott insulator”.
“The Mott criterion: so simple and yet so complex” provides a brief overview of the carrier density-based switching criteria that Mott had proposed.
- Experimental verification. The most study Mott-insulator is Vanadium oxide. Though it is not applicable as an electrical switch (its switching is dictated by thermal activation), VOx is a good platform to study the physics of Mott and Mott-like materials. A very detailed review of switching in VOx can be obtained here. As discussed in the articles, Mott materials can switch with excess carriers through optical generation. The switching in Mott materials is also extremely fast, of the order of femtoseconds.
- CeRAM. The experimental verification of CeRAM by the Symetrix group was performed in 2011. These papers showed modeling, integration process as well as electrical results of early CeRAM devices.
Though there is not enough literature on the theory of carbon-doped transition metal oxides, initial density functional theory work on CO doping of NiO gives insight into the hybridization of molecular orbital before and after such reaction.