Research Groups

The understanding of fundamental, physical processes in quantum materials and the identification of universal aspects among them constitutes a necessary basis for the design of new quantum materials with desired functionalities. Our group investigates the collective behavior of interacting electrons which gives rise to the many fascinating phases of matter in quantum materials. We seek to explain the underlying mechanisms behind the phase formation and to determine characteristic properties of the different phases. We are particularly interested in situations when excitations of different phases strongly interact so that it is essential to consider their mutual influence on each other. This includes, for example, the study of quantum phase transitions or unconventional superconductivity. To account for the decisive role of interactions and the interplay of different degrees of freedom in these complex situations, we employ modern, field-theoretical tools with an emphasis on renormalization group techniques. We make use of microscopic and effective descriptions inspired by experimental observations to obtain a comprehensive picture of correlated phases in quantum materials. more

The focus of Quantum Microscopy and Dynamics group is to integrate the techniques of attosecond physics, scanning tunneling microscopy and ultrafast Raman (coherent) spectroscopy to realize and utilize a space-time quantum microscope to capture electrons and atoms in action in molecules, two-dimensional materials and superconductors. The microscope is capable of probing matter at its fundamental space-time quantum limits, with Ångstrom-scale (spatial), attosecond (time) and millielectronvolt (energy) resolutions, all at the same time. Our group has recently captured real space-time movies of electronic and atomic motion in single molecules. Capturing real-space time images of molecules undergoing chemical (and geometrical) transformations and two-dimensional materials undergoing structural phase transformations will be the key goals the group will pursue in the next few years. The group also pursues experiments on molecules present in the nanocavity of “on-chip” quantum nanodevices exploring different regimes of light-matter interaction and light-driven electron transport through them. more

The Ultra-cold 2D Quantum Matter group investigates the quantum electronic transport and optoelectronics in novel two-dimensional materials, with special emphasis on investigating their superconducting, magnetic, and topological properties. Over the past few years the group has pioneered research into 2D crystalline magnets and 2D topological insulators, as well as the emergent field of strongly correlated physics in moiré quantum matter. Of particular importance was the group’s discovery in 2018 of correlated insulator states and superconductivity in magic angle twisted bilayer graphene. This emergent field, also known as twistronics, makes use of a new and unprecedented knob in materials science, namely the ability to change the relative angle between two 2D crystalline structures. Such changes in twist angle can lead to dramatic modifications of the materials’ electronic structure, which have enabled the realization of most of the quantum phases of matter in this new moiré quantum matter platform. The group's current emphasizes is on discovering new quantum phases that may appear at ultra-cold temperatures, below the currently explored regime.

Research in the Organic Electronics group focuses on novel functional organic materials and on the manufacturing and characterization of organic and nanoscale electronic devices, such as high-performance organic thin-film transistors and integrated circuits. Of particular interest is the use of organic self-assembled monolayers in functional electronic devices. We are developing materials and manufacturing techniques that allow the use of high-quality self-assembled monolayers as the gate dielectric in low-voltage organic and inorganic field-effect transistors and low-power integrated circuits on flexible substrates. We are also studying the use of self-assembled monolayers for the preparation of nanoscale organic/inorganic superlattices that exhibit unique electrical, optical, and mechanical properties. Scientific work in organic electronics is highly interdisciplinary and involves the design, synthesis and processing of functional organic and inorganic materials, the development of advanced micro- and nanofabrication techniques, device and circuit design, and materials and device characterization. more

Materials with strong electronic correlations are amongst the most intriguing topics at the forefront of research in condensed matter physics. On the one hand, they exhibit fascinating phenomena like quantum criticality and high-temperature superconductivity, bearing a high potential for applications. On the other hand, they are theoretically very appealing due to their limited understanding, even on the very fundamental level. Within the research group Theory of Strongly Correlated Quantum Matter, starting from September 2020, the frontier of this fundamental understanding is pushed by applying cutting-edge numerical quantum field theoretical methods to quantum critical systems, high-temperature superconductors, Mott insulators and magnetically frustrated systems, both in the purely model (Hubbard model, periodic Anderson model) as well as material oriented (heavy fermions, cuprates, organics) context. more

Research in the Solid State Nanophysics group focuses on the study of the many unusual ways in which electrons organize themselves as a result of interactions and correlations among their charge and spin degrees of freedom, when these electrons are confined in one or more dimensions on the nanometer scale. Transport and optical properties are investigated with local probe methods, at low temperatures, in high magnetic fields, under high frequency radiation or any combination thereof. The electrons are confined either in III–V semiconductor heterostructures or in strictly two-dimensional crystals such as graphene, molybdenum disulfide or other single layers of the large class of layered materials with weak interlayer forces. Also hybrid stacks of these two-dimensional crystals, so-called van der Waals heterostructures, are fabricated and explored in the quest for novel functionalities and interaction physics as well as for the study of ion diffusion and mixed conduction with the use of miniature galvanic cells. more