Nanostructures can be used to tailor light-matter interaction in many ways. Optical metasurfaces composed of two-dimensional configurations of sub-wavelength sized metallic or dielectric nanostructures in particular have a large range of potential applications, e.g., as perfect absorbers or sensors. Their combination with optoelectronic devices can enable and enhance device functionality. Here, we report on the transfer of prototype device realizations in a university cleanroom to a 200 mm Si BiCMOS pilot line, i.e. the combination of plasmonic nanohole arrays with Ge photodetectors for on-chip refractive index sensing as well as the realization of metasurface-based, wavelength-selective photodetectors on the Si platform. The reproducibility of CMOS-compatible fabrication methods can also leveraged for the realization of metasurfaces with tailored properties for light-matter interaction. We present examples based on plasmonic metasurfaces, whose optical properties are strongly influenced by near-field interactions between the individual meta-atoms. Our results not only highlight challenges and opportunities in implementing metasurfaces as functional device layers, they also showcase the advantages of using high precision Si technology for the fabrication of nanophotonic structures.

The magneto-optic Kerr effect (MOKE) describes the change of polarization state apon reflection of polarized light from a magnetized sample [1]. Initially, this effect has been assumed to be proportional to the magnetization M of the investigated sample and, thus, became a standard tool to study magnetic thin-film systems, e.g. via Kerr spectroscopy, time-resolved MOKE, or Kerr imaging [2,3].

However, in the last two decades contributions of second order in M have been explored [4]. The so-called quadratic MOKE (QMOKE) is proportional to M2 and can be utilized, e.g., to study antiferromagnetic materials [5] since the MOKE linear in M vanishes here due to the antiparallel alignment of the magnetic moments. Recently, we have identified MOKE contributions of third order in magnetization (cubic MOKE, CMOKE) being proportional to M3 [6] and studied its dependence on the structural domain twinning of Ni(111) thin films characterized by off-specular x-ray diffraction mappings.

In my talk, I will introduce higher-order MOKE effects and discuss recent examples. We have investigated the QMOKE in Fe [7] and Heusler compound thin films [8], and confirmed the linear dependence of the QMOKE on the structural order of the Heusler compound in a wide spectral range. We are able to describe the angular dependencies of QMOKE and CMOKE with respect to the crystal orientation of the thin films. For example, while it is quite simple to find CMOKE in (111)-oriented films, it is not straightforward to identify it in (001)-oriented samples [9]. I will discuss the reasons. Finally, I will show that the CMOKE in Co(111) thin films can reach up to 30% of the linear MOKE signal [10] which is promissing for future research applications such as CMOKE microscopy, spectroscopy and pump probe experiments.

Engineering 1D topological superconductivity in a van der Waals heterostructure
The assembly of two-dimensional van der Waals materials into heterostructures provides a versatile platform for the engineering of electronic states via proximity effects, enabling the creation of novel topological phases that do not exist in the individual layers [1,2]. The resulting heterostructure properties are typically well accessible on their surfaces, such that scanning tunneling microscopy (STM) has become an important tool for their structural and electronic characterization. In 2D topological insulator monolayer WTe2 placed on superconducting NbSe2, we observe robust proximity-induced gaps in the bulk as well as the topological edge states [1,3]. Magnetic field-dependent measurements and zero-bias conductance features at magnetic scatterers coupled to the proximitized edge state support the realization of 1D topological superconductivity in this system.
References
1. F. Lüpke et al., Nature Physics 16, 526 (2020)
2. K. Jin et al., Advanced Materials Interfaces 11, 2300658 (2024)
3. J. Martinez-Castro et al., arXiv.2304.08142

The high‐temperature superconducting (HTS) dynamo enables injection of large DC currents into a superconducting coil, without the need for thermally‐inefficient current leads. Because of this important advantage, there is significant interest in using such technology to energise superconducting coils in a range of applications including superconducting rotating machines and NMR/MRI magnets. Numerical modelling has played a key role in elucidating the underlying physics of such devices and several different numerical models have now been developed as useful and cost-effective tools to examine experimental results, as well as optimise and improve dynamo designs. This talk summarises recent developments in this important area, including modelling the open‐circuit voltage behaviour in 2D and 3D, the definition of a new benchmark problem for the HTS modelling community, investigating key dynamo parameters, modelling dynamic coil charging behaviour and calculating losses. Some comments on the future of such modelling is provided, including some outstanding challenges.

Halide perovskites have transformed solar energy, but controlling their properties with precision remains a central challenge. In this talk, I will show how we can move beyond trial-and-error synthesis toward a more predictive and programmable approach to perovskite nanocrystals.
Using chemistry-aware machine learning, we establish a data-efficient framework that enables nanometer-precise control over emission wavelength, linewidth, and quantum yield—effectively allowing us to “dial in” optical properties on demand. Combined with a mechanistic understanding of nanocrystal growth, this provides a pathway toward reproducible and targeted materials design.
But what ultimately determines these optical properties? To answer this, we turn to nanoscale spectroscopy. By systematically varying nanocrystal size and shape, we uncover a surprisingly simple picture: light absorption is governed by volume, while carrier recombination and many-body interactions depend sensitively on geometry. Pushing further, new cavity-enhanced techniques allow us to directly measure absorption at the level of just a few nanocrystals, linking structure, emission, and absorption within the same nanoscale object.
These insights reveal a unifying perspective: precise synthesis and nanoscale physics are not separate challenges, but two sides of the same problem. And together they define how we design the next generation of perovskite optoelectronic materials.

The effects of Cu impurities in bismuth telluride, discovered during thermoelectric device manufacturing, have been known for decades. However, the precise structural site occupied by Cu atoms and its resulting doping mechanism remain unclear. Cu is observed to increase charge carrier concentration in both p- and n-type Bi₂Te₃. This leads to two conflicting hypotheses: (1) Cu intercalates in the van der Waals gaps, acting as an electron donor, or (2) Cu substitutes for Bi/Sb, which would act as an electron acceptor—a model at odds with its n-type doping capability. This talk will elucidate these contradictory findings by employing the framework of defect chemistry. We will use existing experimental data to develop a general model that explains the doping behavior of Cu in bismuth telluride.