Seminar

Understanding structure-property relationships in fields as diverse as nanoscale electronic junctions, heterogeneous catalysis, electrochemistry and energy storage often starts by meeting the challenge of identifying key structure motifs. For the theorist this is followed by tackling the problem of calculating the relevant functional characteristics, also challenging, particularly for excited state properties. I will discuss the modern toolbox for these problems, including a brief outline of the basic physical ingredients of modern manybody perturbation theory which enables studies of excited state properties. I will then discuss its application in the context of the search to develop new materials for use in photocatalysis. In particular, I will discuss the search for key structural motifs at semiconductor-water interfaces and the connection to electrochemical energy level alignment. 

The plethora of fascinating properties observed in oxide heterostructures has attracted a lot of interest. Most noticeably, the confined electron gas formed at the interface between the two insulators LaAlO3 and SrTiO3 features e.g. gate-tunable superconductivity, ferromagnetism and non-volatile memory effects. Numerous studies have been devoted to understanding the origin of the conductivity along with enhancing its properties. Recently, we found that substituting LaAlO3 with γ-Al2O3 can produce a confined electron gas with an electron mobility exceeding 100,000 cm2/Vs. Here, I show that...

How does a microscopic system like an atom or a small molecule get rid of the excess electronic energy it has acquired, for instance, by absorbing a photon? If this microscopic system is isolated, the issue has been much investigated and the answer to this question is more or less well known. But what happens if our system has neighbors as is usually the case in nature or in the laboratory? In a human society, if our stress is large, we would like to pass it over to our neighbors. Indeed, this is in brief what happens also to the sufficiently excited microscopic system. A new mechanism of...

Atomically thin semiconducting crystals derived from new classes of layered materials have rapidly emerged to enable two-dimensional (2D) nanostructures with unusual electronic, optical, mechanical, and thermal properties.  While graphene has been the forerunner and hallmark of 2D crystals, newly emerged 2D semiconductors offer intriguing, beyond-graphene, attributes.  The sizable and tunable bandgaps of compound and single-element 2D semiconductors offer attractive perspectives for strong multiphysics coupling and efficient transduction across various signal domains.  ...

There is considerable excitement about in realizing non-Abelian Anyons, particles whose phase upon exchange depends on the path taken. Their observation signals the emergence of new topological phases and offers a route to quantum computation. I will outline the reasons to expect such particles in a particular quantum spin-liquid, where there is long-range entanglement but no magnetic order. I will then describe a particularly promising van-der-Walls material for realizing such particles, RuCl3. Via Raman spectroscopy, we have uncovered the Fermi statistics emerging from the Majorana...

A recent addition to low-dimensional materials are monolayer transition metal dichalcogenides (TMDs), such as WSe2, with an atomically thin, honeycomb lattice and optical band gaps. In addition to spin, charge carriers in TMDs exhibit a “valley” degree of freedom, which can be optically addressed using circularly polarized light, opening up exciting possibilities for “valleytronics". Another curious aspect of TMDs lies in the non-trivial geometry of their band structure which gives rise to equal but opposite Berry curvature, an effective magnetic field in the momentum...

Dramatic advances in tabletop generation of THz pulses with high field levels have enabled nonlinear THz spectroscopy and THz control over molecules and materials. The most widely used approach for generation of strong fields in the 0.2-2 THz range involves excitation of phonon-polaritons in ferroelectric host crystals, and a THz polaritonics platform has been developed that includes capabilities for THz field control and visualization as well as direct and strong coupling to collective spin waves (magnons). Recent developments in THz generation, nonlinear spectroscopy, and control over...

 ETS transcription factors comprise an evolutionarily related family of genetic regulators that are ubiquitous in animals and control a myriad of physiologically critical processes. ETS proteins are united by a highly conserved DNA-binding domain, with overlapping target DNA preferences on the one hand, but are functionally diverse and non-redundant on the other. This so-called ìspecificity conundrumî besets not only our understanding of ETS homologs but also the structure-activity relationships of eukaryotic transcription factors in general. Translationally, it hampers efforts to develop...

One of the promising routes towards creating novel topological states and excitations is to combine superconductivity and quantum Hall (QH) effect. However, signatures of superconductivity in the QH regime remain scarce, and a superconducting current through a QH weak link has so far eluded experimental observation. By utilizing high mobility graphene/boron nitride heterostructures we demonstrate the existence of a novel type of supercurrent-carrying states in a QH regime at magnetic fields as high as 2 Tesla. At low magnetic fields, devices demonstrate the Fraunhoffer pattern and Fabri-...