Controlling complex systems requires understanding how competing interactions shape their behaviour. A method for engineering an emergent ‘slush’ phase in arrays of Rydberg atoms has been achieved; this state blends liquid-like mobility with solid-like stability. Carefully tuned laser parameters balance nearest-neighbour atomic interactions against frustrating next-nearest neighbour effects, uncovering a dynamic transition between isotropic spreading and one dimensional growth.

Driven-dissipative Rydberg systems are now established as a platform for exploring soft matter physics. The novel “slush” phase in arrays of Rydberg atoms exhibits properties of both liquids and solids simultaneously. Achieving this required balancing attractive forces between the nearest atomic neighbours against frustrating interactions with those further away, a key element for enabling dynamic behaviour. Simulations reveal that carefully controlling these competing effects observed transitions from unrestricted spreading to confined growth within the slush phase, generating complex spatial arrangements and patterns.

A new “slush” phase has been engineered in arrays of Rydberg atoms; this state uniquely combines properties typically associated with both liquids and solids. Simulations reveal these arrangements exhibit spatial correlations similar to observing patterns in a crowd where people tend to cluster around others, indicating relationships even if not directly touching.

Simulations modelled excitation propagation via probabilistic state transitions

Kinetic Monte Carlo simulations revealed how this ‘slush’ phase behaves; these computational experiments tracked how excitation spreads through an array of Rydberg atoms over time. Directly observing such dynamics in a physical system is challenging due to speed and complexity, so researchers used this technique instead. In particular, they didn’t simulate every atom’s movement precisely but modelled it as random “jumps” between states, ground or excited, with probabilities determined by carefully calculated rates dependent on neighbouring atomic configurations.

This simplification allowed exploration of long timescales relevant for understanding kinetic constraints within the system, effectively modelling its evolution without excessive detail. The calculations were performed on a two-dimensional 64×64 site array. A key parameter was eta (η), set at 100, quantifying the strength of next-nearest neighbour interactions causing ‘kinetic frustration’. Simulations incorporating third-nearest neighbour interactions alongside these primary effects showed preservation of key structural features like loopless geometry and dynamical heterogeneity; this suggests that even more complex interaction schemes don’t fundamentally alter observed behaviour.

Extended Observation Reveals Criticality and Frustration in Rydberg Atom Array Dynamics

Observation windows for Rydberg atom array dynamics increased ten-fold, extending from approximately 10 -4 to 10 6 time units through strong dephasing regimes suppressing unwanted decay. This advance enabled detailed study of an emergent “slush” phase where liquid and solid characteristics coexist due to competition between facilitated excitation via nearest neighbour interactions and frustration induced by next-nearest neighbours. Finite size scaling analysis confirmed the system operates near criticality, evidenced by fractal cluster geometries and spatial correlations resembling those found in critical phenomena.

Tuning laser parameters enables dynamics within this Rydberg atom array; residual next-nearest neighbour interactions then induce frustration, a competition between opposing forces. The resulting delicate balance generates an emergent “slush” phase exhibiting both liquid and solid characteristics. This is demonstrated by observing complex spatial arrangements at η values ranging from 10 to 100. Further supporting its operation near criticality is finite size scaling analysis which revealed generalised Ornstein, Zernike correlations similar to other systems undergoing critical transitions.

Controlling Dynamic Transitions in Liquid-Solid Slush Phases

Precise control over a ‘slush’ phase has been demonstrated through careful tuning of atom interactions; this unusual state behaves like both a liquid and solid simultaneously within their experiment. This work offers tantalising prospects for engineering complex materials exhibiting both liquid-like flow and solid stability, though demonstrating broad applicability remains challenging. While simulations successfully tuned dynamics *within* a specific transition between unrestricted spreading and confined growth, it isn’t yet clear how strong this control will be across different system parameters or scales.

These special Rydberg atoms interact strongly when excited by lasers, allowing excitation to spread within arrays with now precise control. By balancing competing interactions between neighbouring atoms, the team created a unique “slush” phase exhibiting characteristics of both liquids and solids simultaneously, a state where energy can flow relatively freely while maintaining some structural stability. This achievement establishes driven-dissipative Rydberg systems as a promising platform for studying complex materials far from equilibrium, offering insights into the emergence of order in active environments.

Through kinetic Monte Carlo simulations, researchers demonstrated an emergent “slush” phase in a two-dimensional array of dissipative Rydberg atoms, a state displaying properties of both liquid and solid configurations. Tuning laser detuning to balance nearest-neighbor interactions facilitated this dynamic behavior; residual next-nearest neighbor interactions introduced frustration that influenced how excitations spread through the system. The resulting dynamics exhibited a crossover between isotropic spreading and one-dimensional growth, generating fractal cluster geometries at η values ranging from 10 to 100. These findings establish driven-dissipative Rydberg systems as a controllable platform for investigating complex nonequilibrium soft matter phenomena.

👉 More information
🗞 Kinetic Slush in Dissipative Rydberg Arrays
✍️ Hufeng Wen, Ya-Xin Xiang, Qun-Li Lei and Zhengyang Bai (Nanjing University); Thomas Pohl (TU Wien); Yu-Qiang Ma
🧠 ArXiv: https://arxiv.org/abs/2610.36661

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