Electron microscopes provide deep insight into the smallest details of matter and can reveal, for example, the atomic configuration of materials, the structure of proteins or the shape of virus particles. However, most materials in nature are not static and rather interact, move and reshape ... more
Shining a light on nanoscale dynamics
Watching metamaterials at work in real time using ultrafast electron diffraction
Physicists from the University of Konstanz, Ludwig-Maximilians-Universität München (LMU Munich) and the University of Regensburg have successfully demonstrated that ultrashort electron pulses experience a quantum mechanical phase shift through their interaction with light waves in nanophotonic materials, which can uncover the nanomaterials' functionality. The corresponding experiments and results are reported in the latest issue of Science Advances.
Nanophotonic materials and metamaterials
Many materials found in nature can influence electromagnetic waves such as light in all different kinds of ways. However, generating novel optical effects for the purpose of developing particularly efficient solar cells, cloaking devices or catalysts often requires artificial structures, so-called metamaterials. These materials achieve their extraordinary properties through sophisticated structuring at the nanoscale, i.e. through a grid-like arrangement of smallest building blocks on length scales well below the wavelength of the excitation.
The characterization and development of such metamaterials requires a deep understanding of how the incident light waves behave when they hit these tiny structures and how they interact with them. Consequently, the optically-excited nanostructures and their electromagnetic near fields must be measured at spatial resolutions in the range of nanometres (~10-9 m) and, at the same time, at temporal resolutions below the duration of the excitation cycle (~10-15 s). However, this cannot be achieved with conventional light microscopy alone.
Ultrafast electron diffraction of optically-excited nanostructures
In contrast to light, electrons have a rest mass and therefore offer 100,000 times better spatial resolution than photons. In addition, electrons can be used to probe electromagnetic fields and potentials due to their charges. A team led by Professor Peter Baum (University of Konstanz) has now succeeded in applying extremely short electron pulses to achieve such a measurement. To that end, the duration of the electron pulses was compressed in time by means of terahertz radiation to such an extent that the researchers were able to resolve the optical oscillations of the electromagnetic near fields at the nanostructures in detail.
High spatial and temporal resolutions
"The challenge involved with this experiment lies in making sure that the resolution is sufficiently high both in space and in time. To avoid space charge effects, we only use single electrons per pulse and accelerate these electrons to energies of 75 kiloelectron volts", explains Professor Peter Baum, last author on the study and head of the working group for light and matter at the University of Konstanz's Department of Physics. When being scattered by the nanostructures, these extremely short electron pulses interfere with themselves due to their quantum mechanical properties and generate a diffraction image of the sample.
Interaction with the electromagnetic fields and potentials
The investigation of the optical-excited nanostructures is based on the known principle of pump-probe experiments. After the optical excitation of the near fields, the ultrashort electron pulse arrives at a defined point in time and measures the time-frozen fields in space and time. "According to the predictions of Aharonov and Bohm, the electrons experience a quantum mechanical phase shift of their wave function when travelling through electromagnetic potentials", explains Kathrin Mohler, a doctoral researcher at LMU Munich and first author on the study. These optically-induced phase shifts provide information about the ultrafast dynamics of light at the nanostructures, ultimately delivering a movie-like sequence of images that reveals the interaction of light with the nanostructures.
A new application regime for electron holography and diffraction
These experiments illustrate how electron holography and diffraction can be harnessed in the future to improve our understanding of fundamental light-matter interactions underlying nanophotonic materials and metamaterials. In the long term, this may even lead to the development and optimization of compact optics, novel solar cells or efficient catalysts.
- real-time analysis
DNA strand breaks can contribute to the development of cancer and the ageing process. Researchers from the Departments of Biology and Chemistry of the University of Konstanz have now been able to observe in real time the molecular processes that take place at DNA strand breaks by means of i ... more
Researchers from the University of Konstanz, Bielefeld University and ETH Zurich demonstrate for the first time that the pulsed EPR technique RIDME (relaxation-induced dipolar modulation enhancement) can be used for in-cell distance determination in biomacromolecules. Applied within the cel ... more
CRISPR-Cas9 can alter genes at pre-defined sites in specific ways, but it does not always act as planned. An LMU team has now developed a simple method to detect unintended ‘on-target’ events, and shown that they often occur in human stem cells. The gene-editing system CRISPR-Cas9 has revol ... more
The interaction between biotin and streptavidin is a well-established experimental tool in bionanotechnology. LMU physicists have now shown that the mechanical stability of the complex is dependent on the precise geometry of the interface. Mechanical forces play a vital role at all levels i ... more
Biomedical researchers at LMU have isolated immune cells from human tonsils obtained following routine surgery, and used them to analyze aspects of the immune response and test the effects of anti-inflammatory agents at the cellular level. Human tissues that have been surgically removed fro ... more
Researchers at the the University of Regensburg and the MPSD in Hamburg have developed a groundbreaking method to detect the dynamics of light on such a small scale with high temporal resolution. Since the 17th century, researchers have explored tiny objects in their most fundamental detail ... more
Proteins, the ubiquitous workhorses of biochemistry, are huge molecules whose function depends on how they fold into intricate structures. To understand how these molecules work, researchers use computer modeling to calculate how proteins fold. Now, a new algorithm can accelerate those vita ... more
Physicists from the University of Regensburg have developed a novel microscope that allows them to record slow-motion movies of tiny nanostructures with groundbreaking time resolution – faster even than a single oscillation cycle of light. With their new microscope they have directly imaged ... more
- 1analytica 2020 with very good results in the digital format
- 2Researchers find the favourite food of an enigmatic intestinal bacterium
- 3Spread of a novel SARS-CoV-2 variant across Europe in summer 2020
- 4How deadly parasites ‘glide’ into human cells
- 5analytica 2020: The world’s largest virtual trade fair for analysis, laboratory technology and biotechnology
- 6New cancer diagnostics: A glimpse into the tumor in 3D
- 7Midbrain organoids for automated chemical screening and disease research
- 8Artificial Intelligence has learned to estimate oil viscosity
- 9Nanopatterns of proteins detected by cryo-electron microscopy
- 10World record resolution in cryo-electron microscopy
- New and highly efficient method for SARS-CoV-2 mutation analysis
- New contrast mechanism improves xenon MRI
- Leverage the huge potential that lies dormant in the vast amounts of lab data generated daily
- A prognostic Alzheimer’s disease blood test in the symptom-free stage
- Hard-magnetic coatings for high-precision microscopy