Dicke-Stark Engine Performance Peaks Near Superradiance, Optimised by Stark Field

The quest for efficient energy conversion drives ongoing research into heat engines, and a new study explores the potential of quantum systems to optimise performance. Weilin Wang, Xiyuan Zhang, Weiran Zhao, et al. from North China Electric Power University present a quantum heat engine based on the Dicke-Stark model, a system exhibiting collective atomic behaviour. Their investigation reveals that carefully controlling the strength of an applied electric field and the interactions within the atomic system allows for significant improvements in the engine’s output work and efficiency, particularly near a ‘superradiant’ point where atoms collectively emit energy. This research demonstrates that tuning these quantum properties, and employing asymmetric operating cycles, offers a pathway to designing high-performance heat engines with enhanced energy conversion capabilities, potentially impacting future technologies in energy harvesting and thermal management.

It employs a finite-size Dicke-Stark model as the working substance, a system that combines the collective behavior of many atoms with the control offered by an external electric field. Through numerical calculations, researchers obtain the complete energy spectrum and behavior of this model, exploring how the strength of the electric field, the interaction between atoms, the duration of specific engine cycles, and the number of atoms influence the engine’s output work, efficiency, and power. The results demonstrate that maximum work and efficiency occur when the engine operates near a critical point, the superradiant phase transition, and that controlling the electric field strength allows for precise tuning of the system.

Quantum Thermodynamics and Open System Dynamics

This body of work provides a comprehensive foundation in quantum thermodynamics and the behavior of open quantum systems, crucial for understanding and optimizing quantum heat engines. Core concepts like relative entropy and quantum information theory establish the theoretical framework for understanding energy transfer at the quantum level, while mathematical tools of open quantum systems, such as Lindblad master equations, model the unavoidable interactions between the engine and its environment, accounting for energy loss and decoherence. Research focuses on how these interactions affect engine performance and how to mitigate their effects. Furthermore, studies explore the limitations and optimizations of thermodynamic cycles operating in finite time, acknowledging that real-world engines cannot operate infinitely slowly, laying the groundwork for understanding the trade-offs between speed and efficiency in quantum engines.

Investigations cover general principles of quantum heat engines, exploring concepts like maximum power and efficiency, and strategies for achieving them, with specific attention given to the quantum Otto cycle and asymmetric cycles, which may offer improved performance. Research also focuses on minimizing energy dissipation, a critical challenge in building practical quantum engines. The Quantum Rabi-Stark model, an extension of the Dicke model incorporating an external electric field, allows for precise control over the system’s properties.

Studies highlight the superradiant phase transition in the Dicke model, a collective emission of light, which is likely a key feature of the engine’s operation. Advanced concepts like counteradiabatic driving, fast equilibration, and Kibble-Zurek scaling offer potential strategies for improving engine performance and understanding its behavior near the critical point. Universal constraints on the efficiency and power of heat engines provide a theoretical framework for optimization. Collectively, this research provides a strong theoretical foundation for building and optimizing quantum heat engines, with a particular emphasis on the Dicke model and its collective behavior. The work addresses key challenges in quantum thermodynamics, such as minimizing dissipation and accounting for environmental interactions, and offers potential strategies for improving engine performance.

Dicke-Stark Model Optimizes Quantum Heat Engine

Researchers are developing quantum heat engines, devices that convert energy at the microscopic level, with the potential to power future nanotechnology. These engines utilize the unique properties of quantum systems to achieve efficiencies beyond those of traditional engines, and recent work focuses on optimizing the materials used as the engine’s core working substance. A promising candidate is a modified Dicke model, incorporating an external electric field, known as the Dicke-Stark model, which allows for precise control over the system’s energy levels and collective behavior. The key to enhancing engine performance lies in maximizing energy output while minimizing energy losses.

Investigations reveal that the most efficient operation occurs when the engine operates near a critical point known as the superradiant phase transition, a state where the system emits a large amount of light due to collective atomic behavior. By carefully tuning the strength of the applied electric field, researchers can precisely control this transition, reducing internal friction and maximizing both the engine’s efficiency and the amount of work it produces, effectively minimizing energy dissipation during operation. The research demonstrates that asymmetric engine designs, where the electric field strength and duration of specific engine cycles differ, further improve performance. Moreover, increasing the number of atoms within the system consistently boosts both energy output and efficiency.

These findings represent a substantial step towards building practical quantum heat engines. By carefully selecting materials and optimizing engine design, researchers are paving the way for microscopic power sources with the potential to revolutionize nanotechnology and beyond. The ability to precisely control quantum systems and minimize energy losses opens up exciting possibilities for efficient energy conversion at the smallest scales.

Dicke-Stark Engine Optimisation and Asymmetry

This research investigates a quantum heat engine employing the Dicke-Stark model as its working substance. Through numerical simulations, the study demonstrates how key parameters influence the engine’s performance, specifically its output work, efficiency, and power. Results indicate that optimizing the interaction between atoms near a superradiant phase transition maximizes both work and efficiency, while adjusting the electric field strength allows for control over the engine’s operating state. Furthermore, increasing the number of atoms within the model also contributes to improved output work and efficiency.

The simulations reveal that asymmetric heat engines, where the expansion and compression processes differ, offer greater potential for optimization. Notably, the duration of specific strokes within the engine cycle, particularly the adiabatic strokes, significantly impacts performance, with targeted adjustments of these timings maximizing both power output and thermodynamic efficiency. The study acknowledges that real-world heat engines operate within finite timeframes, and these simulations provide insights within an idealized framework.