Earthquakes and avalanches may have devastating consequences, yet are hard to study, occurring only occasionally and often in poorly monitored regions. Fortunately, simpler systems with similar properties can sometimes be investigated efficiently and safely in the laboratory to yield generally applicable results in a phenomenon called universality. New research at the DQMP, University of Geneva reveals, however, that transferring such insights from one universal system to another requires a more careful analysis of the magnitude of the probing force used to study the avalanche-like response than previously assumed.
A wide variety of systems, from earthquakes to the evolution of stock market prices can often be described by the same type of statistical equation. In other words, the behaviour of one system can under certain circumstances be directly translated to another. Determining these circumstances is a crucial and complex endeavour.
Dr Philippe Tückmantel, a postdoctoral researcher supervised by Prof. Patrycja Paruch, together with his coworkers at the University of Geneva and at the University of California, Berkeley report on precisely this in their work, recently published in Physical Review Letters. They studied so-called ferroelectric domains, regions where ions in the crystal collectively shift positions in a preferred direction, and which grow under an applied electric field. These domains can be directly imaged using a technique called piezoresponse force microscopy, whose ultra-high resolution allows the observation of events of down to 10 nanometers, revealing the avalanche-like behavior of ferroelectric domain growth. For the first time this avalanche-like behaviour was imaged with such precision. By combining their experimental observations with statistical analyses, the authors show that the equation which characterizes the physics of ferroelectric domains is modified when the electrical force applied to the crystal goes above a certain level. This important result highlights how crucial the probing force is for understanding these laboratory-level systems before general comparisons can be made more broadly to other systems.
Read the article in Physical Review Letters