‘Wave’ Plasmons Proposed to Power a New Class of Sensing and Communication Technologies at Nanoscale

May 22, 2020 by Luke James

A study co-led by Berkeley Lab has shown how wavelike plasmons could be used to power an entire new class of nanoscale sensing and photochemical technologies.

Plasmons are quantum collective motions of electrons in solids which arise from the long-range Coulomb interaction, an experimental law of physics that quantifies the amount of force between two stationary, electrically charged particles. The electric force between charged bodies is called the Coulomb force. 

In atomically thin 2D materials, plasmons have an energy that is useful for applications like sensing and communications. Figuring out how long plasmons last for and whether their energy can be controlled at the nanoscale is something that has eluded scientists until now. According to the Berkeley Lab team’s research, long-lived plasmons have been observed in a new class of conducting transition metal dichalcogenide (TMD) called “quasi 2D crystals”. 


Plasmon waves created by an ultrafast laser.

Plasmon waves created by an ultrafast laser attached to an atomic force microscopy tip. The plasmon waves are the red and blue rings, moving slowly across an atomically thin layer of TMD. Image used courtesy of Berkeley Lab


Understanding How Plasmons Work in ‘Quasi 2D Crystals’

In contrast to previous studies that only looked at conductive electrons, to understand how these plasmons operate in so-called quasi 2D crystals, the researchers characterized the properties of both conductive and nonconductive electrons in a monolayer of the TMD tantalum disulfide. “We discovered that it was very important to carefully include all the interactions between both types of electrons,” said C2SEPEM Director Steven Louie, who led the study. 

To do this, the research team developed new algorithms to compute the material’s electronic properties, including plasmon oscillations with long wavelengths, “as this was a bottleneck with previous computational approaches,” said lead author Felipe da Jornada, who is currently an assistant professor in materials science and engineering at Stanford University. 


More Stable Than Originally Thought

Using these algorithms, the team carried out calculations using the Cori supercomputer at Berkeley Lab’s National Energy Research Scientific Computing Center (NERSC). To their surprise, the results revealed that the plasmons in quasi 2D TMDs are more stable than previously thought, for as long as 2 trillionths of a second. 

According to the researchers, their findings also demonstrate that plasmons generated by these quasi 2D TMDs could be used to enhance the intensity of light by more than 10 million times, potentially giving rise to applications in chemistry and electronics that could be controlled by light.