Researchers from the Institute of Laser Physics at Universität Hamburg have
succeeded for the first time in realizing a time crystal that spontaneously
breaks continuous time translation symmetry. They report their observation
in a study published online by the journal Science on Thursday, 9 June,
2022.
The idea of a time crystal goes back to Nobel laureate Franck Wilczek, who
first proposed the phenomenon. Similar to water spontaneously turning into
ice around the freezing point, thereby breaking the translation symmetry of
the system, the time translation symmetry in a dynamical many-body system
spontaneously breaks when a time crystal is formed.
In recent years, researchers have already observed discrete or Floquet time
crystals in periodically driven closed and open quantum systems. "In all
previous experiments, however, the continuous-time translation symmetry is
broken by a time-periodic drive," says Dr. Hans Keßler from Prof. Andreas
Hemmerich's group at the Cluster of Excellence CUI: Advanced Imaging of
Matter. "The challenge for us was to realize a system that spontaneously
breaks the continuous time translation symmetry."
Using a Bose-Einstein condensate inside an optical high-finesse cavity
In their experiment, the scientists used a Bose-Einstein condensate inside
an optical high-finesse cavity. Using a time-independent pump, they observed
a limit cycle phase which is characterized by emergent periodic oscillations
of the intracavity photon number accompanied by the atomic density cycling
through recurring patterns.
They found that the time phase of the oscillations takes random values
between 0 and 2π, as expected for spontaneously broken continuous symmetry.
By identifying the stability area in the relevant parameter space and
showing the persistence of the limit cycle oscillations even in the presence
of strong temporal perturbations, the researchers demonstrated the
robustness of the dynamic phase.
Reference:
Phatthamon Kongkhambut et al, Observation of a continuous time crystal,
Science (2022).
DOI: 10.1126/science.abo3382
Tags:
Physics