Social Distancing on the Nanoscale
Nanotechnology is already an integral part of modern electronics in our computers, smart phones or cars. The size of electronic components makes conventional optical microscopes no longer sufficient for inspecting these nanostructures. Therefore, scientists have replaced the optical microscope with much more sophisticated concepts, such as electron or scanning tunneling microscopy. However, these techniques use electrons instead of light, which can influence the properties of the nanoscale devices. Furthermore, these important measurement techniques are limited to electrically conducting samples. This study introduced a new technique, which can resolve electron motion on the nanoscale without needing to be electrically contacted. The concept behind the technique works similar to contactless payment, i.e. Near Field Communication (NFC). Better still, the new method also reaches unbelievable time resolution as good as one quadrillionth of a second (the femtosecond timescale).
Combining these extreme spatial and temporal resolutions makes the recording of slow-motion movies of ultrafast electron dynamics on the nanoscale possible.
Further reading: News IDW-online Plankl et al., Nature Photonics 15, 594–600 (2021)
Plankl et al., Nature Photonics 15, 594–600 (2021)
High-Density Exciton Phases
The density-driven transition of an exciton gas into an electron–hole plasma remains a compelling question in condensed matter physics. In two-dimensional transition metal dichalcogenides, strongly bound excitons can undergo this phase change after transient injection of electron–hole pairs. Unfortunately, unavoidable nanoscale inhomogeneity in these materials has impeded quantitative investigation into this elusive transition. This study demonstrates how ultrafast nanoscopy can capture the Mott transition through the density-dependent recombination dynamics of electron–hole pairs within a WSe2 homobilayer.
Ultrafast nanoscopy is a powerful technology to study strong electronic correlations and interlayer coupling within a diverse range of stacked and twisted 2D materials.
Siday et al., Nano Lett. (2022)
Electronic Motion in Nanowires
Modern nanotechnology aims to create artificial materials with novel properties, e.g. semiconductor nanowires for high-speed electronics. To understand the behavior of these structures and to make them even faster, smaller, and more efficient, scientists would like to trace directly how electrons move on length scales of only a few atoms. These processes often occur extremely quickly, which has spurred a drive to develop a microscope that combines excellent spatial resolution with the highest possible temporal resolution. This study trace the time-dependent dielectric function at the surface of a single photoexcited InAs nanowire in all three spatial dimensions.
Besides answering technological questions in electronics and photovoltaics, ultrafast pump-probe nanoscopy provides application potential ranging from novel physical insights into exotic materials to understanding biological processes on the molecular scale.
Eisele et al., Nature Photonics 8, 841–845 (2014)