We propose a theoretical model to study the quantum phase transition in a double-cavity magnonic system. We find that the system exhibits a second-order phase transition from a parity-symmetric phase to a parity-symmetry-broken phase or a first-order phase transition from a parity-symmetric phase to a bistable phase when the driving strength of one cavity is above a critical value. We obtain the phase diagram, the critical point, and the corresponding critical exponent to characterize the phase transition. We can identify different phase transitions by the different behaviors of the mean magnon number and correlation fluctuation in the vicinity of the critical point. In particular, we show that the phase transition in one cavity can be precisely and efficiently controlled by adjusting the parameters of the other cavity, which suggests that we can easily observe the phase transition at low driving strength in experiment. The effects of additional microwave pulses on the dynamical behavior of the phase-transition observable and the experimental feasibility of our theoretical scheme are discussed as well.
We propose a theoretical model to study the quantum phase transition in a double-cavity magnonic system. We find that the system exhibits a second-order phase transition from a parity-symmetric phase to a parity-symmetry-broken phase or a first-order phase transition from a parity-symmetric phase to a bistable phase when the driving strength of one cavity is above a critical value. We obtain the phase diagram, the critical point, and the corresponding critical exponent to characterize the phase transition. We can identify different phase transitions by the different behaviors of the mean magnon number and correlation fluctuation in the vicinity of the critical point. In particular, we show that the phase transition in one cavity can be precisely and efficiently controlled by adjusting the parameters of the other cavity, which suggests that we can easily observe the phase transition at low driving strength in experiment. The effects of additional microwave pulses on the dynamical behavior of the phase-transition observable and the experimental feasibility of our theoretical scheme are discussed as well.
We propose a scheme to engineer the superradiant phase transition (SPT) in cavity magnonics by periodically modulating the frequency of the magnon mode. The studied system is composed of a yttrium iron garnet (YIG) sphere positioned inside a microwave cavity, where magnons in the YIG sphere are strongly coupled to microwave photons. Under the Floquet drive, the effective frequencies of both the cavity and magnon modes can be readily controlled via the frequency and strength of Floquet field. This tunability allows the cavity magnonic system to support a rich steady-state phase diagram, featuring parity-symmetric, parity-symmetry-broken, bistable, and unstable phases. With the increase of Floquet-field strength, the system exhibit a discontinuous phase transition from the parity-symmetric phase to the parity-symmetry-broken phase at a critical threshold, accompanied by an abrupt jump of the magnon occupation from zero to a finite value. Upon further increase of Floquet-field strength, the magnon occupation declines continuously from a nonzero value back to zero, corresponding to a second-order phase transition that restores the parity-symmetric phase. Additionally, fluctuations in magnon number during the SPT process are examined. Our work establishes an alternative route to engineer the cavity-magnon SPT without relying on microwave parametric drive.
Magnons, as quasiparticles arising from spin wave excitations in magnetic materials, have demonstrated significant application potential in quantum information technology, spintronics, and microwave engineering in recent years. The cavity magnon optomechanical system, serving as a key platform for investigating magneto-optical interactions, has advanced the exploration of nonlinear dynamical behaviors and the innovative design of quantum devices through strong coupling between magnons, photons, and phonons. However, traditional single-cavity systems face limitations in terms of tunability, long-range interactions, and nonlinear enhancement, making them insufficient for complex quantum control requirements. In recent years, dual-cavity systems have become a research hotspot due to their multidimensional control capabilities achieved through inter-cavity coupling, such as photon mode splitting and enhanced nonlinear Kerr effects. Meanwhile, semiconductor quantum dots, provide a novel pathway for regulating magnon dynamics due to their tunable nonlinear response characteristics. In this work, we construct a novel coupled quantum system by integrating quantum dots and a dual-cavity architecture, and investigate the bistable phenomena under both forward and backward driving field inputs. By comparing the third-order nonlinear equations governing magnon populations in the two scenarios, we derive the impedance matching condition. When this condition is satisfied, the magnon responses induced by forward driving field and backward driving field are identical. Conversely, under impedance mismatch, the magnon responses exhibit different behaviors. Specifically, when the impedance matching condition is violated, the dual-cavity magnon optomechanical system incorporating three-level quantum dot molecules exhibits a lower bistability threshold than its counterpart without quantum dots. This allows for a transition from low steady state to high steady state while reducing the driving field strength, thereby achieving switching functionality at lower input power. Furthermore, we establish a multiparameter cooperative control model, revealing a three-dimensional parameter space formed by tunneling coupling, cavity-quantum dot coupling, and inter-cavity coupling. By adjusting these coupling strengths, the bistability threshold and hysteresis loop width can be effectively controlled, thereby modulating the driving field intensity required for bistability. This system is expected to experimentally observe the magnonic bistability through the vector network analyzer-based detection of abrupt changes in transmission or absorption windows in reflection spectra. Such capabilities can advance data signal transmission, switching devices, and memory technologies, and has the potential to serve as components of large-scale quantum information processing units. Additionally, this research may find important applications in the field of magnetic spintronics.
The emerging hybrid cavity optomagnonic system is a very promising quantum information processing platform for its strong or ultrastrong photon-magnon interaction on the scale of micrometers in the experiment. In this paper, the superfluid--Mott-insulator quantum phase transition in a two-dimensional cavity optomagnonic array system has been studied based on this characteristic. The analytical solution of the critical hopping rate is obtained by the mean-field approach, second-order perturbation theory, and Landau second-order phase transition theory. The numerical results show that the increasing coupling strength and the positive detunings of the photon and the magnon favor the coherence and then the stable areas of Mott lobes are compressed correspondingly. Moreover, the analytical results agree with the numerical ones when the total excitation number is lower. Finally, an effective repulsive potential is constructed to exhibit the corresponding mechanism. The results obtained here provide an experimentally feasible scheme for characterizing the quantum phase transitions in a cavity optomagnonic array system, which will offer valuable insight for quantum simulations.
Abstract In this work, we investigate quantum phase transitions (QPTs), dynamical chaos and Loschmidt echo (LE) behaviors in a parametrically driven cavity-magnon hybrid system. The system consists of a yttrium iron garnet microsphere coupled to a microwave cavity with a squeezed cavity field generated via an optical parametric amplification process, and is described by an extended Tavis–Cummings model. Using the Holstein–Primakoff (HP) transformation and displacement transformation, we derive the ground-state energy function and obtain the phase diagram. The results show that the system undergoes a second-order QPT between the normal phase and the superradiant phase in the thermodynamic limit. Once the system enters the SP region, this design will induce a strong nonlinearity, thereby exhibiting significant chaotic dynamic behavior, verified by the Poincaré section method. Furthermore, we introduce the LE method to this hybrid system in order to characterize its QPT behaviors. With the assistance of the auxiliary atoms, the observable parameter LE exhibits consistency with the QPT laws, which can be used to effectively detect the critical behavior of this magnon-photon system. This work reveals the laws of phase transitions, dynamical chaos and LE behaviors in a parametrically driven cavity-magnon hybrid system, providing a theoretical basis for simulating and exploring quantum critical phenomena, nonlinear behaviors and quantum measurements in hybrid magnon systems.
Abstract We theoretically investigated the influence of an atom’s third energy level on quantum phase transitions in a Ξ-type atom-cavity quantum electrodynamics system driven by a coherent field. Through numerical simulations, we demonstrate that for a resonant two-level atom, the critical driving strength for quantum phase transitions scales linearly with the atom-cavity coupling strength. Analysis of the Wigner function confirms the occurrence of first-order quantum phase transitions, characterized by the emergence of coexistence states and symmetry breaking. Introducing a third atomic energy level under resonant conditions inhibits such phase transitions; however, detuning this level under specific parameters promotes them. By modulating the detuning of the third energy level, one can effectively control the critical conditions for quantum phase transitions in this system. These findings hold potential of applications in optically controlled phase transitions, precision measurements, and laser physics.
Preparing magnon nonclassical states is a central topic in the study of quantum magnonics. Here we propose to generate magnon squeezed states in a hybrid cavity-magnon-qubit system by engineering an effective Rabi-type magnon-qubit interaction. This is achieved by adiabatically eliminating the cavity mode and driving the qubit with two microwave fields, of which the driving frequencies and amplitudes are properly selected. By operating the system around the critical point associated with the ground-state superradiant phase transition in the normal phase, a magnon parametric amplification-like interaction is induced, leading to a dynamical magnon squeezing. We further analyze the effects of the dissipation, dephasing, and thermal noise on the magnon squeezing. Our results indicate that a moderate degree of squeezing can be produced using currently available parameters in the experiments.