Home

Research interests:

Here is a quick list summarizing my key research interests:

• Strongly correlated quantum many-body systems

• Quantum simulation with ultracold atoms and photons

• Many-body systems with topological order

• Fractional quantum Hall effect & frustrated quantum magnets

• Interacting electrons and high-temperature superconductivity

• Non-equilibrium dynamics in quantum systems

• Impurity and polaron physics

Here is a more detailed summary of my research accessible also for non-experts:

The main goal of my research is to learn more about nature. As a condensed-matter physicist, this primarily means I am interested in the behavior of exotic phases of matter. Sometimes interactions become dominant and they determine all key properties of a physical phase. Such effects can have immediate practical relevance, like in the case of high-temperature superconductors, or they can be more of academic interest. Often one can't even tell, and problems that are considered of purely academic interest suddenly turn out to be of immense practical importance, or real-world observations pose immense challenges in their theoretical explanation.

There are many ways to make progress in understanding strongly correlated materials, ranging from purely experimental approaches to highly developed mathematical treatments. My research is theoretical, but with a strong connection to ongoing experiments. Besides consistent theoretical descriptions of physical effects I'm always searching for clear and simple explanations. This approach is particularly powerful in the context of quantum simulations, where the underlying models are very well defined and elementary enough to uncover the most fundamental mechanisms how nature works.

With the introduction of a variety of quantum simulation platforms during the last decade - ranging from ultracold atoms and strongly interacting photons to arrays of superconducting qubits - my generation of physicists has the unique opportunity to explore strongly correlated many-body systems from an entirely new perspective. Not only can the most interesting model systems, like the two-dimensional Fermi-Hubbard Hamiltonian, be studied. New experimental capabilities also allow to directly measure exotic non-local order parameters and resolve quantum effects taking place inside complicated many-body systems on the level of single particles on individual lattice sites.

The theoretical approaches used in my research are directly related to the new experimental capabilities. To fully understand the behavior of a system as a whole, it is crucial to understand its microscopic details. One promising strategy is to start by studying impurity physics. For example, a single hole inside an anti-ferromagnet can be understood as an impurity. When it becomes mobile it interacts with the surrounding spin system, and these interactions strongly modify (or dress) its properties. Loosely speaking, a high-temperature superconductor is obtained when the number of holes in such a system is increased. One of my long-term research goals is to develop a better microscopic  understanding of high-temperature superconductivity which fully includes the mechanisms that dress a single hole inside an anti-ferromagnet.

Impurities can behave very differently depending on the many-body system through which they are moving. In my research I am interested as much in the properties of the impurities themselves, as in the properties of the surrounding many-body systems. Examples include spin-full impurity particles inside fractional quantum Hall systems or quantum spin liquids (with possible applications for topological quantum computation), light atoms interacting strongly with a surrounding Bose-Einstein condensate or impurities inside strongly correlated one-dimensional systems. My most recent research focuses on light holes doped into quantum magnets and their role in the problem of understanding high-temperature superconductivity and the elusive pseudogap phase in particular.