Long-range Coupling Achieves Integrability Breaking and Drives Chaotic Dynamics in Spin Chains
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Understanding how complex systems transition from ordered to chaotic behaviour remains a fundamental challenge in physics, and recent work by Y. S. Liu, X. Z. Zhang, and colleagues sheds new light on this process.
The team investigates a one-dimensional spin model with interactions extending over long distances, revealing how these interactions govern the shift between predictable, ordered states and unpredictable chaos, even when the system operates beyond the usual constraints of conventional physics. Through careful analysis of the system’s energy levels and how information spreads within it, the researchers demonstrate that the strength of these long-range interactions acts as a key control parameter, dictating the onset of chaos in both standard and non-standard systems. Remarkably, they also identify a set of stable states that resist this descent into chaos, maintaining coherence and offering potential pathways for preserving delicate quantum information within complex environments. Long-Range Interactions and Quantum System Dynamics Scientists are unraveling the mechanisms that cause order to break down in complex quantum systems, a central challenge in modern physics.
This research investigates a one-dimensional spin model featuring tunable long-range interactions, which connect distant parts of the system.
The team explores how these interactions influence the system’s behaviour and its transition from predictable to chaotic dynamics, examining both standard and non-standard quantum systems. The study demonstrates that increasing the range of these interactions significantly alters the system’s energy levels and wave functions, ultimately leading to the breakdown of predictable behaviour. This breakdown is characterised by the appearance of level repulsion and the emergence of chaotic dynamics, indicating a shift towards a more complex and unpredictable state and bridging the gap between orderly and chaotic regimes. Through a systematic analysis of energy level spacing and entanglement, the researchers demonstrate that the strength of these long-range interactions acts as a universal control parameter driving the transition from order to quantum chaos. Specifically, increasing the interaction strength induces a crossover from predictable to chaotic behaviour, both in standard and non-standard quantum systems. Most remarkably, the team identified a unique set of quantum states that resist this disorder. These states, termed “scar states”, survive as robust quantum many-body scars, retaining low entanglement and coherent behaviour even under strong perturbations. Quantum Chaos and Many-Body System Studies This research focuses on understanding the behaviour of many interacting quantum particles, a fundamental area of condensed matter physics and quantum information science. A significant theme is the study of quantum chaos, investigating how classical chaotic behaviour manifests in quantum systems by examining the statistical properties of energy levels and the sensitivity to initial conditions. Scientists are increasingly using a tool called Krylov complexity to characterize the complexity of quantum states and the dynamics of quantum systems, finding it useful for probing quantum chaos and identifying different phases of matter. There is also growing interest in systems where the Hamiltonian is not standard, exhibiting unusual behaviour such as enhanced sensitivity to perturbations. Researchers are employing platforms like ultracold atoms and trapped ions to simulate quantum many-body systems, and utilising computational tools to perform detailed calculations. The study focuses on spin models, commonly used to investigate magnetism and quantum phase transitions. A key aspect is the study of open quantum systems, which interact with their environment, representing a more realistic scenario. Scientists analyse energy level spacing to identify signatures of quantum chaos, utilise mathematical structures called Krylov subspaces to approximate the evolution of quantum states, and explore exceptional points, singularities in the energy spectrum of non-standard systems. Long-Range Interactions Drive Quantum Chaos and Scars This research demonstrates a universal connection between long-range interactions and the breakdown of predictable dynamics in complex quantum systems. Scientists investigated a spin model where the strength of interactions between distant parts of the system could be carefully controlled, revealing how this control bridges the gap between orderly and chaotic behaviour. Through detailed analysis of energy levels and quantum entanglement, they established that increasing the range of these interactions triggers a transition from predictable to chaotic dynamics, both in standard and non-standard quantum systems. Remarkably, despite the emergence of overall chaos, the team identified a special set of quantum states that resist this disorder. These states, termed “scar states”, maintain low entanglement and coherent behaviour even under strong perturbations, representing a surprising exception to the usual tendency towards thermalization. This discovery offers a new pathway for preserving quantum coherence in complex systems, potentially relevant to areas such as quantum information processing and materials science. The authors acknowledge that their model represents a simplified representation of real materials, and future work will focus on extending these findings to more complex and realistic scenarios. They also suggest exploring the potential for manipulating these scar states for practical applications in quantum technologies. 👉 More information 🗞 Integrability Breaking and Coherent Dynamics in Hermitian and Non-Hermitian Spin Chains with Long-Range Coupling 🧠 ArXiv: https://arxiv.org/abs/2512.14065 Tags: