A New State of Light 一 Researchers Observe New Phase in Bose-Einstein Condensate of Light Particles

A single "super photon" is made up of many thousands of individual light particles. Around ten years ago, researchers from the University of Born created a single super photon, an extreme aggregate photon state, a completely new light source. This aggregate state is known as optical Bose-Einstein condensate. It has captivated many physicists ever since this exotic world is home to its own physical phenomena, which has sparked a lot of interest.

The Bose-Einstein condensate is a gas of atoms that is so dense and cold that its matter waves lose their individuality and condense into a superatom wave.

Satyendra Nath Bose and Albert Einstein predicted it in the 1920s. It was eventually created in the lab in the 1990s at the University of Colorado Boulder, MIT, and Rice University using laser cooling evaporative cooling techniques.

In 2010, Professor Martin Weitz of the University of Bonn's Institute of Applied Physics and colleagues created the first Bose-Einstein condensate from photons.

Prof. Dr. Martin Weitz and theoretical physicist Prof. Dr. Johann Kroha have returned from their latest "expedition" into the quantum world with an extraordinary observation. They describe a previously undiscovered phase transition in the optical Bose-Einstein condensate. This is referred to as an overdamped phase.

A Bose-Einstein condensate (BEC) is the fifth state of matter in condensed matter physics. Because the particles in this state behave like a single massive superparticle, the state can also be described as a single wave function.

The Bose-Einstein condensate is a rare physical state that occurs only at shallow temperatures very close to absolute zero (-273.15 °C, -459.67 °F).

Recently physicists discovered an overdamped phase in the photon Bose-Einstein condensate coupled to the environment in their new experiments, researchers explained.

“The somewhat translucent mirrors cause photons to be lost and replaced, resulting in a non-equilibrium that causes the system to lose temperature and oscillate.”

“This results in a transition from this oscillating phase to a damped phase. The amplitude of the vibration decreases when it is damped.”

“The overdamped phase we observed corresponds to a new state of the light field, so to speak,” said team member Fahri Emre ztürk, a doctoral student at the Institute for Applied Physics at the University of Bonn.”

“The laser's effect is distinguished by the fact that it is usually not separated from that of the Bose-Einstein condensate by a phase transition, and there is no sharply defined boundary between the two states. This means that physicists can switch back and forth between effects indefinitely.”

“However, in our experiment, the overdamped state of the optical Bose-Einstein condensate is separated from both the oscillating state and a standard laser by a phase transition,” Professor Weitz explained.

“This demonstrates the presence of a Bose-Einstein condensate, which is a distinct state from the standard laser.”

“In other words, we're dealing with two distinct phases of the optical Bose-Einstein condensate.”

Researchers are now excited to use this research to investigate new states of the light field in multiple coupled light condensates, resulting in the system.

The research was published in the journal Science.