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Weird science: Scientists find new way molecules can cooperate at room temperature

What if glowing molecules could synchronize, much like fireflies flashing in unison? Researchers have discovered that molecules confined within tiny gold nanostructures can behave collectively, coordinating their interactions even under conditions where this was previously thought impossible. The finding challenges longstanding assumptions about how optical coherence forms and opens new possibilities for highly sensitive sensors, molecular photonics, and future quantum technologies capable of operating at room temperature.

Optical coherence describes a state in which light -- or the molecules producing it -- behaves in a highly coordinated way. It is the principle behind technologies such as lasers, advanced imaging systems, and quantum communication. Traditionally, scientists believed this kind of coordinated behavior required specially designed optical cavities that trap light for relatively long periods.

In the new study, published in Nature Nanotechnology, researchers showed that the molecules confined inside tiny gaps between gold nanoparticles (known as plasmonic cavities) can synchronize their behavior even though light escapes from the system extremely quickly. This finding could contribute to new ways to build synchronized states of matter such as superfluids at room temperature, and potentially be applied for advanced sensing, molecular photonics, and quantum devices.

Schematic of plasmonic nanocavities containing synchronized dipoles, with levitated insets showing luminescence from molecular emitters, and the first order spatial coherence image. [Credit: Image © Dr Rakesh Arul/Courtesy of University of Cambridge]

 

 

 

 

To investigate this, the researchers placed luminescent molecules inside gaps less than a billionth of a meter wide between gold nanoparticles and illuminated them with a continuous laser while observing how the molecules emitted light.

"By increasing the power of a laser, we observed the molecules switching from acting independently to behaving collectively," said lead author Dr. Rakesh Arul, research fellow at the Cavendish Laboratory. "At low laser power, the emitted light came only from the illuminated spot. As the power increased, the emission spread into a glowing halo far outside the laser beam, revealing that molecules separated by large distances were beginning to act together."

The light the molecules emitted spread far beyond the illuminated area, while measurements confirmed that the molecules had become synchronized across the sample.

"What emerged was a synchronized dipole state where many molecules oscillate together as though they are acting as a single collective system, despite the fact that photons escaped from the system extremely quickly," said Arul.

Unlike a conventional laser, however, the emitted light did not become highly focused. The coordination existed mainly between the molecules themselves, while the light quickly lost its coherence after leaving the nanocavities.

To understand what was happening, the researchers combined laser excitation, interferometry, and theory to look for evidence that the molecular dipoles were becoming synchronized. In collaboration with Dr. Piper Fowler-Wright and Prof. Jonathan Keeling in the University of St. Andrews, state-of-the-art quantum optical theory was used to explain the results and reveal the source of synchronization. They found that coherence arose because the molecules synchronized directly with one another through strong electromagnetic interactions within the tiny gaps between neighboring gold nanoparticles, rather than through photons bouncing back and forth inside an optical cavity. Using interferometry, the researchers found that the molecules developed spatial coherence across the sample.

During the research, the scientists also saw spiral-like phase patterns called vortices. This indicates that, even when the system is synchronized, it still undergoes complex and interesting dynamic behavior rather than settling into a simple, uniform state.

"The most surprising part was that this happened at room temperature in a highly disordered system where photons leak away extremely quickly -- exactly the kind of environment where coherence is normally expected to disappear," added Prof. Jeremy Baumberg, who led the research at the Cavendish Laboratory.

"This is exciting because plasmonic nanocavities are not just enhancing molecular emission; they are mediating interactions between molecules and making them behave collectively, even in environments that were previously considered too disordered. This opens up a way to study coherent many-body physics in simply-assembled room-temperature materials," said Baumberg.

The researchers now plan to explore how changing the size of the nanogaps, molecule density, disorder, and optical coupling affect the synchronized state. They also want to explore other emitters, including molecular qubits and color centers, to see whether plasmonic nanocavities can enable future room-temperature quantum photonic platforms.

Source: University of Cambridge

Published August 2026

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