#plasmons

New electron microscopy technique reveals complex spin structures at femtosecond timescales

Plasmons are collective oscillations of electrons in a solid and are important for a wide range of applications, such as sensing, catalysis, and light harvesting. Plasmonic waves that travel along the surface of a metal, called surface plasmon polaritons, have been studied for their ability to enhance electromagnetic fields. One of the most powerful tools for studying these waves is time-resolved electron microscopy, which uses ultrashort laser pulses to observe how these plasmonic waves behave. An international research team recently pushed the boundaries of this technique. As reported in Advanced Photonics, the researchers used multiple time-delayed laser pulses of four different polarizations to capture the full electric field of these waves. This method allowed them to achieve a level of accuracy previously not possible.

Looking for elusive quantum particles? Try a bad metal, researchers suggest

Metals, as most know them, are good conductors of electricity. That's because the countless electrons in a metal like gold or silver move more or less freely from one atom to the next, their motion impeded only by occasional collisions with defects in the material. There are, however, metallic materials at odds with our conventional understanding of what it means to be a metal. In so-called "bad metals"—a technical term, explains Columbia physicist Dmitri Basov—electrons hit unexpected resistance: each other. Instead of the electrons behaving like individual balls bouncing about, they become correlated with one another, clumping up so that their need to move more collectively impedes the flow of an electrical current. Bad metals may make for poor electrical conductors, but it turns out that they make good quantum materials. In work published on February 13 in the journal Science, Basov's group unexpectedly observed unusual optical properties in the bad metal molybdenum oxide dichloride (MoOCl2).

Scientists uncover light absorbing properties of achiral materials

Researchers at the University of Ottawa have made a discovery that changes what we know about light and materials. They found that engineered achiral (symmetric) materials, called achiral plasmonic metasurfaces, can absorb light differently depending on the handedness of the wavefront of light. This was surprising because, for years, such materials were found to be indifferent to any optical probes and do not show such selective absorption. The research, conducted over the past year at uOttawa's Advanced Research Complex (ARC), was led by Ravi Bhardwaj, Professor, Department of Physics at the University of Ottawa and Ph.D. student Ashish Jain. Collaborators include Howard Northfield, Research Engineer, and colleagues Ebrahim Karimi, Canada Research Chair in Structured Light and Associate Professor of Physics, and Pierre Berini, University Research Chair in Surface Plasmon Photonics and Professor of Electrical Engineering.

Reducing energy loss in metal nanostructures by altering geometrical dimensions

Researchers at City University of Hong Kong (CityUHK) have made a discovery that significantly reduces energy loss in metal nanostructures. By altering the geometrical dimensions of these structures, researchers have unlocked their full potential, paving the way for the development of more powerful and efficient nanoscale optical devices. The research team is co-led by Professor Tsai Din-ping, Chair Professor in the Department of Electrical Engineering at CityUHK, and Professor Yuri Kivshar, from Australian National University. Professor Kivshar also served as a visiting research fellow at the Hong Kong Institute for Advanced Study at CityUHK in 2023. "This breakthrough resolves the longstanding issue of energy loss, allowing for high-performance nanoscale optical devices," said Dr. Liang Yao, from the Department of Electrical Engineering at CityUHK, who is the first author of the research article titled "From Local to Nonlocal High-Q Plasmonic Metasurfaces," published in the journal Physical Review Letters.

Researchers identify unique phenomenon in Kagome metal

In traditional Japanese basket-weaving, the ancient "Kagome" design seen in many handcrafted creations is characterized by a symmetrical pattern of interlaced triangles with shared corners. In quantum physics, the Kagome name has been borrowed by scientists to describe a class of materials with an atomic structure closely resembling this distinctive lattice pattern. Since the latest family of Kagome metals was discovered in 2019, physicists have been working to better understand their properties and potential applications. A new study led by Florida State University Assistant Professor of Physics Guangxin Ni focuses on how a particular Kagome metal interacts with light to generate what are known as plasmon polaritons—nanoscale-level linked waves of electrons and electromagnetic fields in a material, typically caused by light or other electromagnetic waves. The work was published in Nature Communications.

Researchers find a way to reduce the overheating of semiconductor devices

The demand to shrink the size of semiconductors coupled with the problem of the heat generated at the hot spots of the devices not being effectively dispersed has negatively affected the reliability and durability of modern devices. Existing thermal management technologies have not been up to the task. Thus, the discovery of a new way of dispersing heat by using surface waves generated on the thin metal films over the substrate is an important breakthrough.

KAIST announced that Professor Bong Jae Lee's research team in the Department of Mechanical Engineering succeeded in measuring a newly observed transference of heat induced by "surface plasmon polariton" in a thin metal film deposited on a substrate for the first time in the world.

Surface plasmon polariton (SPP) refers to a surface wave formed on the surface of a metal as a result of strong interaction between the electromagnetic field at the interface between the dielectric and the metal and the free electrons on the metal surface and similar collectively vibrating particles.

A New Way to Synthesize Hydrocarbons Could Reduce CO2 Emissions and Slash Costs of Chemical Manufacturing

Room Temperature Conversion of CO2 to CO

New method could potentially reduce carbon dioxide emission into the atmosphere and slash costs of chemical manufacturing.

Researchers at the National Institute of Standards and Technology (NIST) and their colleagues have demonstrated a room-temperature method that could significantly reduce carbon dioxide levels in fossil-fuel power plant exhaust, one of the main sources of carbon emissions in the atmosphere.

Although the researchers demonstrated this method in a small-scale, highly controlled environment with dimensions of just nanometers (billionths of a meter), they have already come up with concepts for scaling up the method and making it practical for real-world applications.

Plasmon-coupled gold nanoparticles useful for thermal history sensing

Researchers have demonstrated that stretching shape-memory polymers embedded with clusters of gold nanoparticles alters their plasmon-coupling, giving rise to desirable optical properties. One potential application for the material is a sensor that relies on optical properties to track an object or environment's thermal history.   

At issue is a stretchable polymer embedded with gold nanospheres. If the material is heated and stretched, followed by cooling to room temperature, the material will hold its stretched shape indefinitely. Once reheated to 120 degrees Celsius, the material returns to its original shape.

But what's really interesting is that the gold nanospheres are not perfectly dispersed in the polymer. Instead, they form clusters, in which their surface plasmon resonances are coupled. These plasmon-coupled nanoparticles have optical properties that shift depending on how close they are to each other, which changes when stretching alters the shape of the composite.