The intertwining of multiple order parameters is a widespread phenomenon in equilibrium condensed matter systems, yet its exploration is often hindered by the complexity of real materials. Here, we present a controlled study of intertwined orders in a minimal and versatile driven-dissipative quantum-engineered platform. We consider a Bose-Einstein condensate at the intersection of two optical cavities, realizing two competing copies of a Z 2 symmetry-breaking superradiant phase transition characterized by density-wave orders. Using periodic drives that exploit dynamical symmetry reduction, we show that collective excitations can be harnessed to stabilize a variety of out-of-equilibrium intertwined orders. Going beyond the conventional phenomenology involving Landau orders, we show the emergence of a larger class of out-of-equilibrium intertwined phases, including intertwining of purely time-crystalline orders, as well as between Landau and time crystal orders. These results should be observable in state-of-the-art experimental setups.
The intertwining of multiple order parameters is a widespread phenomenon in equilibrium condensed matter systems, yet its exploration is often hindered by the complexity of real materials. Here, we present a controlled study of intertwined orders in a minimal and versatile driven-dissipative quantum-engineered platform. We consider a Bose-Einstein condensate at the intersection of two optical cavities, realizing two competing copies of a Z 2 symmetry-breaking superradiant phase transition characterized by density-wave orders. Using periodic drives that exploit dynamical symmetry reduction, we show that collective excitations can be harnessed to stabilize a variety of out-of-equilibrium intertwined orders. Going beyond the conventional phenomenology involving Landau orders, we show the emergence of a larger class of out-of-equilibrium intertwined phases, including intertwining of purely time-crystalline orders, as well as between Landau and time crystal orders. These results should be observable in state-of-the-art experimental setups.
A class of systems exists in which dissipation, external drive and interactions compete and give rise to non equilibrium phases that would not exist without the drive. There, phase transitions could occur without the breaking of any symmetry, yet with a local order parameter, in contrast with the Landau theory of phase transitions at equilibrium. One of the simplest driven dissipative quantum systems consists of two-level atoms enclosed in a volume smaller than the wavelength of the atomic transition cubed, driven by a light field. The competition between collective coupling of the atoms to the driving field and their cooperative decay should lead to a transition between a phase where all the atomic dipoles are phaselocked and a phase governed by superradiant spontaneous emission. Here, we realize this model using a pencil-shaped cloud of laser cooled atoms in free space, optically excited along its main axis, and observe the predicted phases. Our demonstration is promising in view of obtaining free-space superradiant lasers or to observe new types of time crystals.
Cavity quantum electrodynamics (QED) with quantum emitters coupled to resonators provides a powerful platform for engineering light-matter interactions and exploring collective phenomena. In particular, superradiance, arising from collective quantum interference among emitters, has been explored as a route to ultrastable continuous radiation. However, engineering superradiance in the time domain to realize periodic pulsed sources or frequency combs remains largely unexplored. Here, we investigate the non-equilibrium many-body dynamics of a driven spin ensemble coupled to an on-chip superconducting resonator and uncover a dynamical phase transition from continuous-wave to periodic pulsed superradiant emission. To quantitatively capture the observed dynamical phases, we introduce a driven-dissipative cavity-QED model that elucidates how the periodic pulsed superradiant phase emerges from collective, periodically repeating spin dynamics stabilized by the interplay of coherence growth, disorder, and dissipation. We also find that rare-earth ion spin systems exhibiting both optical and microwave transitions enable phase-synchronized, dual-rail superradiant frequency combs in both the microwave and optical domains. Our results not only open new avenues for dual-rail frequency-comb applications in quantum metrology and information processing, but also establish a fundamental connection between periodic pulsed superradiance and the emergence of a continuous time crystal as a novel nonequilibrium phase in driven open systems.
Periodic driving of strongly correlated systems has led to outstanding discoveries from light-induced superconductivity to time crystals. To gain insights into the fundamental nature of these phenomena, we have recently studied the effects of an external periodic driving in a well-controlled yet simple many-body platform consisting of a Bose-Einstein condensate inside a high-finesse optical cavity. This system hosts a competition between a homogeneous condensate phase and a self-organized density wave phase, which manifests in a superradiant phase transition as the intensity of a transverse pump beam is increased. We demonstrate dynamical control of this phase transition by periodic driving of the pump laser. Furthermore, we discover the emergence of genuine dynamical phases, namely a discrete time crystalline phase and nonequilibrium density wave orders. Accompanying experimental results confirm our theoretical predictions about light-induced control in the atom-cavity system.
Modern quantum platforms such as superconducting circuits offer exciting opportunities for the experimental exploration of driven-dissipative many-body systems in unconventional regimes. One such regime arises in bosonic systems, where driving and dissipation can nowadays be engineered through pairs of excitations, rather than through conventional single-excitation or linear processes. These platforms also enable collective rather than local pair loss, so that excitations emitted into the environment originate from a coherent superposition of lattice sites rather than any specific site. In this work, we analyze the superfluid phases accessible to bosonic arrays subject to these novel mechanisms, which are more characteristic of quantum optics, and show that they lead to remarkable spatiotemporal properties beyond the traditional scope of pattern formation in either condensed-matter systems or nonlinear optics alone. In particular, we show that, even in the presence of residual local loss, the system is stabilized into an exotic state in which bosons condense along the modes of a closed manifold in Fourier space. A weak bias drive controls the population distribution across these modes, providing access to a wealth of patterns: from periodic and quasiperiodic structures with tunable spatial wavelengths to condensates that uniformly populate the closed Fourier manifold. Furthermore, when residual local linear dissipation is balanced by pumping, new constants of motion emerge that can force the superfluid to oscillate in time, through a mechanism analogous to that underlying recently discovered superfluid time crystals. Finally, we propose a specific experimental implementation for exploring this rich and unusual spatiotemporal superfluid behavior.
We demonstrate dynamical control of the superradiant transition of cavity-BEC system via periodic driving of the pump laser. We show that the dominant density wave order of the superradiant state can be suppressed, and that the subdominant competing order of Bose-Einstein condensation emerges in the steady state. Furthermore, we show that additional, nonequilibrium density wave orders, which do not exist in equilibrium, can be stabilized dynamically. Finally, for strong driving, chaotic dynamics emerge.
We propose to combine Bose-Einstein condensation in higher Bloch bands and a driven-dissipative cavity-BEC system into a hybrid light-matter platform. Specifically, the condensate is trapped in a bipartite s-px-py-lattice, with a tunable energy offset. This enables a controlled population transfer from the s-orbital to the nearly degenerate px and py orbitals. The system forms a chiral ground state with px±ipy symmetry, with staggered orbital currents. By increasing the transverse pump strength, we drive the system into the superradiant phase, resulting in a self-organized, density checkerboard, which rectifies the staggered chiral order into a topological superfluid state. Using truncated Wigner simulations and complementary mean-field analysis, we determine the phase transition into this state as first order. Our results show that higher-band condensates coupled to a cavity provide a promising platform for engineering non-trivial orbital order and topological superfluid phases in quantum optical many-body systems.