Analysis of the history and prospects of left-handed materials

"Left-handed material" refers to a material whose dielectric constant and magnetic permeability are both negative. When electromagnetic waves propagate, the relationship between the wave vector k, electric field E and magnetic field H conforms to the left-hand law, so it is called "left-handed material". It has strange physical properties such as negative phase velocity, negative refractive index, ideal imaging, inverse Doppler frequency shift, anomalous Cerenkov radiation, etc. "Left-handed material" reverses the "right-hand law" of physics, which describes the relationship between the electric field and the magnetic field and the direction of their fluctuations.

Left-handed materials - originated from the hypothesis of scientists in the 1960s

Since the beginning of this century, an artificial composite material called "left-handed material" has begun to gain more and more popularity in the fields of solid physics, materials science, optics and applied electromagnetism, and research on it is showing a rapid development trend. However, its emergence originated from the hypothesis of scientists in the former Soviet Union in the 1960s.

In physics, the dielectric constant ε and the magnetic permeability μ are the two most basic physical quantities that describe the properties of electromagnetic fields in homogeneous media. In the known material world, for dielectrics, the dielectric constant ε and the magnetic permeability μ are both positive, and the electric field, magnetic field and wave vector form a right-handed relationship. Such materials are called right-handed materials (RHM). This right-hand rule has always been considered the norm in the material world, but this norm began to encounter subversive challenges in the 1960s. In 1967, the former Soviet physicist Veselago published a paper in an academic journal in the former Soviet Union, reporting for the first time his new discovery of the electromagnetic properties of matter in theoretical research, namely: when ε and μ are both negative, the electric field, magnetic field and wave vector form a left-handed relationship. He called this hypothetical material left-handed material (LHM), and pointed out that the behavior of electromagnetic waves in left-handed materials is opposite to that in right-handed materials, such as negative refraction of light, negative Cherenkov effect, inverse Doppler effect, etc. This paper attracted the attention of a British person and was translated into English and republished in another former Soviet physics academic journal in 1968. However, few people realized that a new page had been opened in the world of materials.

Since the salient feature of left-handed materials is that their dielectric constant and magnetic permeability are both negative, some people also call them "double negative media (materials)", and they are also commonly called "negative refractive index materials", or simply "negative materials".

Left-handed materials: A breakthrough at the beginning of this century sparked people's imagination

The research and development of left-handed materials has not been smooth sailing. In the thirty years since this subversive concept was proposed, although it has many novel properties, it has only remained in theory and no actual left-handed materials have been found in nature. Therefore, this bizarre hypothesis was not immediately accepted, but was almost ignored until the end of this century. The reason is that British scientist Pendry and others proposed an ingenious design structure in 1998-1999 that can achieve negative dielectric constant and negative magnetic permeability. Since then, people have begun to invest more and more interest in this material. The breakthrough in 2001 has gradually made the research on left-handed materials present a whirlwind in the world.

In 2001, David Smith and other physicists from the University of California, San Diego, based on the suggestions of Pendry and others, used copper-based composite materials to create for the first time a material with negative dielectric constant and negative magnetic permeability in the microwave band. They emitted a beam of microwaves into an artificial medium composed of copper rings and copper wires, and the microwaves were deflected at a negative angle, thus proving the existence of left-handed materials.

In July 2002, scientists at the ETHZ laboratory in Switzerland announced the creation of three-dimensional left-handed materials, which could have a significant impact on the electronic communications industry. The relevant research results were also published in the American "Applied Physics Letters" that month.

At the end of 2002, Professor Jinou Kong of MIT theoretically proved the rationality of the existence of left-handed materials, and said that this artificial medium can be used to manufacture highly directional antennas, focus microwave beams, realize "perfect lenses", and be used for electromagnetic wave stealth, etc. The prospect of left-handed materials began to arouse endless imagination in academia, industry, and especially the military.

2003 was a year of many breakthroughs in left-handed material research. Two groups of researchers led by C. Parazzoli of Boeing Phantom Works in Seattle, USA and G. Eleftheriades of the Department of Electrical Engineering at the University of Toronto, Canada, directly observed the law of negative refraction in experiments; S. Foteinopoulou of Iowa State University also published theoretical simulation results of left-handed materials using photonic crystals as the medium; E. Cubukcu and K. Aydin of the Massachusetts Institute of Technology published an article in Nature magazine, describing the experimental results of the negative refraction phenomenon of electromagnetic waves in two-dimensional photonic crystals. Based on the many discoveries of scientists, the development of left-handed materials has been listed in the top ten scientific advances in the world in 2003 as selected by the American magazine Science, attracting global attention.

In 2003, the research team led by Professor Wu Qun of Harbin Institute of Technology carried out comprehensive research on left-handed materials. So far, in the field of left-handed materials, they have undertaken 4 National Natural Science Foundation projects and 2 sub-projects of the National 973 Project; published 57 SCI-indexed papers and 103 EI-indexed papers in first-class international and domestic academic journals, won 4 outstanding paper awards and 4 special invited reports at international and domestic academic conferences; published 1 academic monograph funded by the National Defense Science and Technology Publishing Fund; and authorized 2 invention patents. The main research directions cover four aspects: "Analysis of the excitation mechanism and electromagnetic characteristics of left-handed materials", "Construction and verification of excellent left-handed materials", "Application of left-handed materials in new microwave devices" and "Stealth technology based on left-handed materials".

In 2004, Shanghai scientists began to appear in the international academic community. After two years of research and ingenious design, the research team led by Professor Zi Jian of Fudan University, the chief scientist of the "973" photonic crystal project, successfully realized the left-handed medium super-plane imaging experiment using the surface wave scattering of water. The paper was published in the famous American Physical Review, which immediately attracted great attention from the academic community and was recommended as one of the focus news of Nature magazine. The research team headed by Professor Chen Hong of the Bohr Solid State Physics Institute of Tongji University began to study left-handed materials in 2001. After two years of research, they have made significant progress in basic theory and material preparation and characterization. The results were published in famous international physics journals. In 2004, they gave a plenary report at the International Microwave and Millimeter Wave Technology Conference and will give an invited report at the International Microwave and Optical Technology Symposium held in Japan in 2005.

In early 2009, Duke University in the United States and Southeast University in China cooperated to successfully develop a new type of "invisible cloak" in the microwave band. This research result was published in the "Science" magazine published at the beginning of the year. As the deputy director of the National Key Laboratory of Millimeter Waves at Southeast University, Professor Cui Tiejun has made many original research results in the fields of computational electromagnetics and new artificial electromagnetic materials. Professor Cui Tiejun's research group and Professor Smith's research group at Duke University began to cooperate in 2006 and achieved a series of results in the theoretical analysis, design, experiment and application of new artificial electromagnetic materials, laying a solid foundation for the development of new "invisible cloaks".

In November 2009, a research team led by Cui Tiejun and Cheng Qiang from the State Key Laboratory of Millimeter Waves at Southeast University successfully produced an artificial electromagnetic collector, which can absorb microwaves in the microwave environment like a "black hole" in the universe. This achievement has attracted great attention from the world's scientific and technological community. On October 15, the Nature website also introduced this research achievement with the title "Scientists Develop Portable Black Hole".

Left-handed materials have rapidly become a research hotspot in the scientific community since the beginning of this century. According to incomplete statistics, the number of research papers on left-handed materials published in major international academic journals in 2000 and 2001 was 13 and 17 respectively, which rose to 60 in 2002 and more than 100 in 2003.

Left-handed materials - the realization of manufacturing has great application prospects

The huge application prospects of left-handed materials stem from their manufacturing realization. In 2000, Pendry suggested making a "super lens" (also known as an "ideal prism") to realize the application of left-handed materials. This suggestion became a reality in 2004. Scientists have successfully made a flat microwave lens using left-handed materials. In February 2004, physicists from the Institute of Theoretical and Applied Electromagnetism in Moscow, Russia announced that they had successfully developed a lens with super resolution, but their technology required that the object being observed almost touch the lens, which made it difficult to operate in practical applications. In the same year, scientists from the University of Toronto in Canada created a left-handed lens, whose working principle is related to rays with microwave wavelengths, which are located close to radio waves in the electromagnetic spectrum. The research results of scientists from the two countries have been highly praised by the scientific community and were rated by the American Physical Society as the most influential research progress of the International Physical Society in 2004.

In addition, based on the extraordinary properties of left-handed materials, scientists have predicted that they can be applied to the design of communication systems and data storage media to create smaller mobile phones or storage media with larger capacity; the equivalent negative refractive medium circuit can effectively reduce the size of the device, widen the bandwidth, and improve the performance of the device. In the future, left-handed materials will play an important role in the development of wireless communications.

Left-handed materials - included in the 2005 National Natural Science Foundation of my country's key project guide

The research on left-handed materials has attracted the attention of the relevant scientific community in my country. In addition to scientists in Shanghai, scientists from the Hong Kong University of Science and Technology, the Institute of Physics of the Chinese Academy of Sciences, Nanjing University, Peking University, Northwestern Polytechnical University and other institutions have also been involved in research in this field. The National Natural Science Foundation of China has included the research on left-handed materials and negative refraction effects in the 2005 key cross-cutting project guidelines. In the theme of "Several Frontier Topics in Quasi-Phase Matching Research" jointly organized by the Department of Mathematics and Physics and the Department of Engineering and Materials, "Research on Basic Issues Related to Left-Handed Materials" is listed as one of the main exploration contents. In the theme of "New Photonic Properties of Periodic and Non-Periodic Microstructures" jointly organized by the Department of Mathematics and Physics and the Department of Information Science, "Research on Negative Refraction Effects in Periodic and Non-Periodic Microstructures in Terahertz, Near-Infrared and Visible Bands" is listed as one of the main exploration contents. At the same time, the Department of Information Science of the Foundation has included "Basic Research on Theory and Application of Metamaterials" in the 2005 Key Project Guidelines. Metamaterials are another name for left-handed materials.