In 2012, Nobel Prize winner Frank Wilczek asked a fascinating question: Could there be a “time crystal,” an object that repeats itself in time just like regular crystals repeat in space?
For years, this idea caused much debate among scientists.
Some thought time crystals were impossible, while others looked for ways to make them under special conditions.
Recently, researchers at Tsinghua University in China, with help from TU Wien in Austria, have successfully created a time crystal using giant atoms called Rydberg atoms.
This achievement has been published in the journal Nature Physics.
To understand this, let’s first look at regular crystals. These are structures where atoms are arranged in a repeating pattern in space. Wilczek’s idea was to find a system that repeats itself in time, without any external influence setting the rhythm.
A clock’s ticking is a familiar example of periodic movement in time, but it doesn’t happen on its own. Someone has to start the clock. In contrast, a time crystal would start its periodic movement spontaneously, without any initial push. This phenomenon is known as “spontaneous symmetry breaking.”
Professor Thomas Pohl from the Institute of Theoretical Physics at TU Wien explains that in a time crystal, the periodicity should arise naturally. The ticking of the time crystal is determined by the physical properties of the system, but the exact times when these ticks occur are random.
In the experiment at Tsinghua University, laser light was directed into a glass container filled with rubidium gas. The strength of the light that emerged from the other end was measured. This setup is usually static, meaning no specific rhythm is imposed on the system. However, the researchers noticed that the light intensity started to oscillate in regular patterns.
The key to this discovery was preparing the atoms in a special way. Electrons can orbit an atom’s nucleus at different distances depending on their energy. By adding energy to the outermost electron, it can move very far from the nucleus, creating what are known as Rydberg atoms. These atoms have giant electron shells, making them several hundred times larger than usual.
When the atoms in the glass container are in these Rydberg states, the forces between them become very strong. This changes how they interact with the laser light. If the laser is set to excite two different Rydberg states in each atom simultaneously, a feedback loop is created. This loop causes the atoms to oscillate between the two states, leading to oscillating light absorption.
These giant atoms naturally fall into a regular beat, which is then seen in the rhythm of the light intensity coming out of the glass container.
Professor Pohl notes that this new system closely aligns with Frank Wilczek’s original idea and provides a powerful platform for further studying time crystals. This discovery could have practical applications, such as creating precise, self-sustained oscillations for use in sensors. Rydberg atoms have already been used successfully in other advanced technologies.
In summary, scientists have taken a significant step forward by creating a time crystal with giant atoms, opening new doors in the field of physics.
Source: KSR.
