In PGI-3 we use our background in surface science and nanoscience to pursue the primary goal of quantum nanoscience: the manipulation and exploitation of quantum-coherent functionality in nanostructures. Our research thus contributes to the foundations of emerging quantum technologies, in particular quantum sensing and quantum computing at the nanoscale. It ranges from the development of new instrumentation, via the fabrication and study of quantum materials, nanostructures and nanodevices, to fundamental experiments that explore the laws of quantum mechanics in previously unexplored regimes.
A recent highlight in the field of new instrumentation is the Jülich Quantum Microscope, an ultra-high vacuum scanning probe microscope (SPM) that reaches a base temperature of 30 mK. It employs adiabatic demagnetisation refrigeration (ADR), which offers several advantages: easy and ultra-precise temperature regulation, absence of circulating liquids, vibration-free environment, ultra-low noise levels, modularity for fast and easy adaption to new scanning probe methods. This unique instrument will be commercialised.
In the field of quantum materials, we investigate heterostructures of two-dimensional van der Waals (vdW) materials, from insulating to superconducting and magnetic. We have continued to advance our fabrication techniques to the point where, very important for scanning tunneling microscopy (STM), complete in-situ preparation is now possible from air-sensitive materials while maintaining atomically clean surfaces and interfaces. Our particular interest is in proximity, twisting and Moiré effects, topological superconductivity, and local transport in topologically protected quantum spin Hall edge states which we want to detect in multi-tip nanoscale transport experiments. Our ultimate goal is the realisation, investigation and manipulation (fusion, braiding) of Majorana states in these designer materials.
Along a different line, we have developed a comprehensive conceptual framework for the manipulation of single molecules with scanning probe microscopes. It is based on formulating the manipulation problem as a Markov decision process (MDP). The framework allows us to create unprecedented nanostructures on a surface or on the tip of a SPM. Its capabilities range from hand control of the molecule with real-time configuration monitoring (based on based on a machine-learned model of the junction) in a virtual reality environment, to autonomous molecular nanofabrication with reinforcement learning.
A widely noted accomplishment is the development of atomic-scale quantum devices at the tip apices of scanning tunneling or atomic force microscopes. These devices are fabricated by bottom-up by molecular manipulation from single atoms and molecules. Based on these devices, we have introduced novel, quantitative scanning probe microscopies, such as scanning quantum dot microscopy (SQDM), which we now use to investigate quantum materials. A very recent breakthrough in this context is the development of a fully integrated and mobile quantum sensor at the tip of an STM that is addressable by single-spin electron spin resonance (ESR) while at the same time providing sub-Ångström spatial resolution. In addition to enabling magnetic resonance imaging (MRI) of almost any quantum material, it can serve as a coherently controllable qubit. As such, it can be used as an initialisation and read out unit in surface-based quantum simulators, as well as a mobile qubit in multi-qubit arrays.
A focal point in our efforts to explore the laws of quantum mechanics in previously unexplored regimes is the Orbital Cinema project, in which we aim to resolve the orbital dynamics of electrons at their intrinsic time scales down to attoseconds. Orbital cinematography combines lightwave electronics with photoemission orbital tomography which we have developed over the last 15 years with our collaborators Michael G. Ramsey and Peter Puschnig at the University of Graz and which allows the 3D imaging of molecular orbitals. In a much-noted proof-of-principle experiment, we performed a two-photon photoemission experiment to trace orbital images on ultrafast timescales. In Orbital Cinema, we aim to record slow-motion movies of molecular orbitals during charge transfer processes, surface chemical reactions, and wave packet motion driven by lightwaves.
The research of the institute department is (or was) recently supported by, amongst others, two ERC grants (starting grant of Christian Wagner, synergy grant of Stefan Tautz as coordinator together with Rupert Huber, Ulrich Höfer and Peter Puschnig), a Heisenberg Professorship (Markus Ternes), and an Emmy Noether Young Investigator Group (Felix Lüpke).
The institute department maintains strategic partnerships with several world-leading research groups, among them the IBS Center for Quantum Nanoscience at Ewha Woman University in Seoul, South Korea, and the Regensburg Center for Ultrafast Nanoscopy (RUN) at the University of Regensburg.