# New Phases and Phase Transitions

Quantum many-body systems are more than the sum of their parts. These systems require a quantum statistical description in the presence of interaction and correlations in order to understand how collective behavior and functionality emerge from the interaction of the many building constituents. It is a central focus of the activities in physics in Hamburg not only to understand the resulting collective features, but also how they emerge dynamically, since nature is not static.

The underlying principles of emergence are key to the modern understanding of condensed matter physics. Starting from pioneering works of Pauli, Bethe and Bloch, the modern quantum theory of materials elucidates the underlying basic principles governing new phases of matter. Also, in high-energy physics, the notion of phases of matter is central, for instance, for the process of the formation of a black hole. Hence, the terms of phases and phase transitions form an overarching link with common theoretical concepts in these fields.

The WPC activities in the pillar New Phases and Phase Transitions comprise:

- Quantum many-body systems far from thermal equilibrium and their dynamics
- Theory of hard condensed matter systems
- Dynamical concepts of topology
- Nonequilibrium quantum phase transitions
- Spectroscopy of quantum many-body systems
- Hybrid quantum systems such as atom-optomechanical systems
- Conformal field theories
- Molecular and nanoscale spintronics

Groups working in this field:

Lichtenstein, Pfannkuche, Potthoff, Thorwart, G. Rohringer, Rubio, Sentef, Herrmann, Mathey, Schmelcher, Bester, Schomerus, ...