1 research outputs found
Emergence of continuous rotational symmetries in ultracold atoms coupled to optical cavities
We investigate the physics of a gas of ultracold atoms coupled to three
single-mode optical cavities and transversely pumped with a laser. Recent work
has demonstrated that, for two cavities, the symmetries of
each cavity can be combined into a global symmetry. Here, we show that
when adding an extra cavity mode, the low-energy description of this system can
additionally exhibit an rotational symmetry which can be spontaneously
broken. This leads to a superradiant phase transition in all the cavities
simultaneously, and the appearance of Goldstone and amplitude modes in the
excitation spectrum. We determine the phase diagram of the system, which shows
the emergence and breaking of the continuous symmetries and displays first- and
second-order phase transitions. We also obtain the excitation spectrum for each
phase and discuss the atomic self-organized structures that emerge in the
different superradiant phases. We argue that coupling the atoms equally to
different modes will in general generate a global symmetry if the mode
frequencies can be tuned to the same value