Clerc Marcel G, Kowalczyk Michał, Zambra Valeska
Departamento de Física and Millennium Institute for Research in Optics, FCFM, Universidad de Chile, Casilla 487-3, Santiago, Chile.
Departamento de Ingeniería Matemática and Centro de Modelamiento Matemático (UMI 2807 CNRS), Universidad de Chile, Casilla 170 Correo 3, Santiago, Chile.
Sci Rep. 2020 Nov 9;10(1):19324. doi: 10.1038/s41598-020-75165-8.
Matter under different equilibrium conditions of pressure and temperature exhibits different states such as solid, liquid, gas, and plasma. Exotic states of matter, such as Bose-Einstein condensates, superfluidity, chiral magnets, superconductivity, and liquid crystalline blue phases are observed in thermodynamic equilibrium. Rather than being a result of an aggregation of matter, their emergence is due to a change of a topological state of the system. These topological states can persist out of thermodynamics equilibrium. Here we investigate topological states of matter in a system with injection and dissipation of energy by means of oscillatory forcing. In an experiment involving a liquid crystal cell under the influence of a low-frequency oscillatory electric field, we observe a transition from a non-vortex state to a state in which vortices persist, topological transition. Depending on the period and the type of the forcing, the vortices self-organise, forming square lattices, glassy states, and disordered vortex structures. The bifurcation diagram is characterised experimentally. A continuous topological transition is observed for the sawtooth and square forcings. The scenario changes dramatically for sinusoidal forcing where the topological transition is discontinuous, which is accompanied by serial transitions between square and glassy vortex lattices. Based on a stochastic amplitude equation, we recognise the origin of the transition as the balance between stochastic creation and deterministic annihilation of vortices. Numerical simulations show topological transitions and the emergence of square vortex lattice. Our results show that the matter maintained out of equilibrium by means of the temporal modulation of parameters can exhibit exotic states.
处于不同压力和温度平衡条件下的物质呈现出不同的状态，如固态、液态、气态和等离子态。在热力学平衡中可观察到物质的奇异状态，如玻色 - 爱因斯坦凝聚态、超流性、手性磁体、超导性和液晶蓝相。它们的出现并非物质聚集的结果，而是由于系统拓扑状态的变化。这些拓扑状态可以在热力学平衡之外持续存在。在此，我们通过振荡强迫来研究一个具有能量注入和耗散的系统中物质的拓扑状态。在一个涉及在低频振荡电场影响下的液晶盒的实验中，我们观察到从非涡旋状态到涡旋持续存在的状态的转变，即拓扑转变。根据强迫的周期和类型，涡旋会自组织，形成方形晶格、玻璃态和无序涡旋结构。通过实验表征了分岔图。对于锯齿形和方形强迫，观察到连续的拓扑转变。对于正弦强迫，情况发生了巨大变化，此时拓扑转变是不连续的，伴随着方形和玻璃态涡旋晶格之间的系列转变。基于一个随机振幅方程，我们认识到这种转变的起源是涡旋的随机产生和确定性湮灭之间的平衡。数值模拟显示了拓扑转变和方形涡旋晶格的出现。我们的结果表明，通过参数的时间调制维持在非平衡状态的物质可以呈现出奇异状态。
