Abstract
The phenomenon of group motion is common in nature, ranging from the schools of fish, birds and insects, to avalanches, landslides and sand drift. If we treat objects as collectively moving particles, such phenomena can be studied from a physical point of view, and the research on many-body systems has proved that marvelous effects can arise from the simplest individuals. The motion of numerous individuals presents different dynamic phases related to the ordering of the system. However, it is usually difficult to study the dynamic ordering and its transitions through experiments. Electron bubble states formed in a two-dimensional electron gas, as a type of electron solids, can be driven by an external electric field and provide a platform to study the dynamic collective behaviors. Here, we demonstrate that the noise spectrum is a powerful method to investigate the dynamics of bubble states. We observed not only the phenomena of dynamically ordered and disordered structures, but also unexpected alternations between them. Our results show that a dissipative system can convert between chaotic structures and ordered structures when tuning global parameters, which is concealed in conventional transport measurements of resistance or conductance. Moreover, charging the objects to study the electrical noise spectrum in collective motions can be an additional approach to revealing dynamic ordering transitions.
Highlights
Collective motions are ubiquitous in creature behaviors and our daily life, and physics has turned out to be a unique tool to probe the complex consequences from simple units [1]
Typical examples include multi-electron bubbles forming on the helium surface [8, 9] and electron solids such as Wigner crystals [10] and bubble states [11,12,13,14] forming in two-dimensional electron gas (2DEG), which are all composed of charged units with spatial periodicity
When a strong external electric field is applied, localized electron solids will be collectively depinned from their localized sites, offering examples of collective motions based on charged units [15,16,17,18,19,20,21,22]
Summary
Collective motions are ubiquitous in creature behaviors and our daily life, and physics has turned out to be a unique tool to probe the complex consequences from simple units [1]. When a strong external electric field is applied, localized electron solids will be collectively depinned from their localized sites, offering examples of collective motions based on charged units [15,16,17,18,19,20,21,22]. Dynamic ordering transitions are expected to happen [23], yet lack direct experimental evidence Such a behavior is reminiscent of the pattern formation behavior in dynamic granular systems [28,29,30] as a non-equilibrium physics problem [31]
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