Non-equilibrium phase transitions in open quantum systems with several absorbing states

具有多个吸收态的开放量子系统中的非平衡相变

• 批准号: 435696605
• 负责人: Professor Igor Lesanovsky
• 金额: --
• 依托单位: Institut für Theoretische Physik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/435696605?language=en
• 关键词: Non; equilibrium; phase; transitions; open

Many-body system are intriguing as they can exhibit collective behaviour that is very challenging to predict even when the interactions between fundamental constituents are precisely known. Direct manifestations of collective effects are phase transitions, for example the conversion of a substance from a liquid to a solid phase at low enough temperature. The latter falls into the class of equilibrium phase transitions. Here the state of the system is determined by so-called detailed balance conditions and typically a temperature can be defined. A lot is known about the general classification of phases and phase transitions in this scenario.Far more interesting are so-called non-equilibrium phase transitions. Here, the concept of a unique temperature is typically not applicable and detailed balance conditions are broken. A paradigmatic set of systems that fall into this class are ones that feature absorbing states. These are configurations that can be accessed by the dynamics, but once they have been reached an escape is no longer possible. An example is given by the population dynamics of bacterial colonies where proliferation and death compete. Once all bacteria are dead, the colony is extinct, and to come back from this absorbing state is no longer possible.In the context of condensed matter and statistical physics absorbing state processes have attracted much attention because they can show new types of collective behaviour. Observed features may fall outside the above-mentioned class of equilibrium processes of which the liquid-solid phase transition is one example. Even more interesting is the situation where the microscopic processes are “quantum” in the sense that non-classical effects such superpositions and entanglement play a part in the dynamics. Such scenario is extremely challenging to study as numerical simulations become extremely demanding due an exponential increase of the required computational resources. Moreover, analytical approaches have not reached a degree of maturity that permits to fully understand and classify emerging phases and phase transitions.This project aims at breaking new ground in our understanding of non-equilibrium quantum many-body physics by conducting a systematic study of systems with two or more absorbing states. This effort will deliver progress in the development of numerical and analytical techniques. Moreover, it aims to uncover dynamical collective phenomena, explore the role of symmetres and to classify non-equilibrium phases and transitions among them. The results are expected to be of relevance for a broad range of scientists working on quantum physics, statistical mechanics and – more broadly – conduct research on systems far from equilibrium.

多体系统是耐人寻味的，因为它们可以表现出集体行为，即使在基本成分之间的相互作用是精确已知的情况下，预测也是非常具有挑战性的。集体效应的直接表现是相变，例如，物质在足够低的温度下从液体转化为固体。后者属于平衡相变的范畴。这里，系统的状态由所谓的详细平衡条件确定，并且通常可以定义温度。在这个场景中，关于相和相变的一般分类已经知道了很多。更有趣的是所谓的非平衡相变。在这里，唯一温度的概念通常不适用，详细的平衡条件被打破。属于这一类的一组典型系统是以吸收状态为特征的系统。这些都是动态可以访问的配置，但一旦达到这些配置，就不再可能逃脱。一个例子是细菌菌落的种群动态，其中增殖和死亡竞争。一旦所有的细菌都死了，菌落就灭绝了，从这种吸收状态中恢复过来就不再可能了。在凝聚态和统计物理的背景下，吸收状态过程引起了人们的极大关注，因为它们可以显示出新类型的集体行为。观察到的特征可能不属于上述平衡过程的类别，液-固相变就是其中的一个例子。更有趣的是，微观过程是“量子”的，因为这种非经典效应的叠加和纠缠在动力学中起着一定的作用。这种情景的研究极具挑战性，因为由于所需计算资源的指数增长，数值模拟变得极其苛刻。此外，分析方法还没有达到可以完全理解和分类新兴相和相变的成熟程度。本项目旨在通过对具有两个或更多吸收态的系统进行系统研究，在我们对非平衡量子多体物理的理解方面取得新的突破。这一努力将在发展数值和分析技术方面取得进展。此外，它的目的是揭示动态集体现象，探索对称性的作用，并对非平衡相和它们之间的转变进行分类。预计这些结果将对从事量子物理、统计力学以及更广泛地研究远离平衡的系统的科学家具有重要意义。