Nanoscale slots enable room-temperature hybrid states of matter in perovskite

Atoms in crystalline solids sometimes vibrate in unison, giving birth to emerging phenomena called phonons. Since these collective vibrations give rhythm to the way in which heat and energy move through materials, they play a central role in devices that capture or emit light, such as solar cells and LEDs.

A team of researchers from Rice University and collaborators has found a way to make two different phonons in thin movies of lead halo, Perovskite interacts with the light so strongly that they merger in entirely new hybrid matter. The observation, reported in a study published in Nature communicationsCould provide a new powerful lever to control how perovskite materials harvest and transport energy.

To obtain a specific light frequency in the Terahertz range to interact with the phonons in halogenure perovskitis crystals, the researchers made nanometric machines – each about a thousand times thinner than a sheet of food film – in a thin layer of gold. The slots acted as tiny metallic traps for light, adjusting its frequency to that of the phonons and thus giving a large form of interaction known as “ultrastrong coupling”.

“To our knowledge, this is the first demonstration at room temperature in a thin film by Pérovskite where two phonons enter the ultra -string coupling diet with a unique Terahertz resonance,” said Dasom Kim, a former rice doctoral student who is a first author of the study.

In order to adjust the effect, the researchers made nanoslots of seven different sizes: longer slots trapped by low frequency light, while the shortest have trapped higher frequencies. The objective was to correspond with precision to the frequency of light confined to the frequencies of vibration of the Pérovskite material.

“We have made nanometric slot tables with seven slightly different lengths to adjust a single Térahertz resonance and deposited thin films from Pérovskite on the top,” said Kim. “The conception of the geometry of the location allowed us to shape the interaction between light and perovskite phonons without using high power laser pulses or bulky crystals.”

The gain was the appearance of three distinct hybrid quantum states called phonon -ocolarritons, each a new mixture of vibrations and light.

“The coupling ratio has reached around 30% of the frequency of phonons at room temperature,” said Kim.

The ability to stage such strong exotic interactions between several quantum modes without resorting to external driving factors opens the door to new ways of piloting the energy flow in opterylectronics.

The experimental results were validated by digital simulations and a theoretical quantum model, which allowed the researchers to calculate the actual coupling forces and to confirm that the two phonon modes operated in the ultrastrastrong coupling diet.

“The progress of nanofabrication and the quality of the film of Pérovskite has made it possible to reach this diet reliably,” said Kim.

“This offers a gentle way and compatible with a device to influence the processes that matter for light harvest and light emissions, potentially improving performance and reducing energy losses,” said Junichiro Kono, Karl F. Hasselmann and author of the study.

“What distinguishes this result is that we were able to discover a completely new phonon behavior without extreme conditions simply by carefully designing the environment on a nanometric scale,” added Kono, who is also director of the Smalley-Curl Institute in Rice.