When a crystal is hit by an intense ultrashort light pulse, its atomic structure is set in motion. A team of scientists from the Max Planck Institute of Quantum Optics (MPQ), the Technischen Universität München (TUM), the Fritz-Haber Institute in Berlin (FHI) and the Universität Kassel can now observe how the configuration of electrons and atoms in titanium dioxide, a semiconductor, changes under the impact of an ultraviolet laser pulse, confirming that even subtle changes in the electron distribution caused by the excitation can have a considerable impact on the whole crystal structure.
Picture 1: An ultraviolet light pulse hits the titanium dioxide crystal. The laser pulse induces a redistribution of weakly bound electrons, which leads to a shift of the equilibrium position of the atoms in the crystal lattice.
Picture 2: Schematic representation of the experiment. An extremely short ultraviolet pulse creates hot excited electrons in the semiconductor titanium dioxide. This changes the spatial distribution of the electrons within the lattice, resulting in a shift of the potentials for the atomic cores, i.e., their rest position (central picture). The subsequent cooling of the electrons, which takes about 20 femtoseconds, further amplifies this effect (right picture). The combined effect of electron excitation and cooling leads to a force on the oxygen atomic cores, resulting in a coherent oscillation within the crystal structure.
Knowledge regarding the interaction between light and solid matter on an atomic scale is still comparable to a map with many blank spots. A number of phenomena are still waiting to be observed or understood. A new, up to date unknown aspect of the interplay between light and matter has now been examined by a team of scientists at the Max Planck Institute of Quantum Optics (MPQ), the Technischen Universität München (TUM), the Fritz-Haber Institute in Berlin (FHI) and the Universität Kassel using intensive ultraviolet laser pulses with only a few femtoseconds duration (one femtosecond is a millionth of a billionth of a second).The physicists illuminated a titanium dioxide crystal (consisting of titanium and oxygen atoms) with an intense ultraviolet laser pulse of less than five femtoseconds duration. The laser pulse excites the valence electrons in the crystal and generates a small number of hot electrons with a temperature of several thousand Kelvin. Valence electrons are electrons that are only weakly bound to the atoms in a crystal that interact strongly with each other and therefore form the bond between the atoms in a crystal. The continuous interplay between the positions of the atomic cores and the valence electrons determines the material characteristics such as electric conductivity, optical properties or the crystal lattice structure.
Dr. Olivia Meyer-Streng | Max-Planck-Institut
Telescopes team up to study giant galaxy
12.12.2017 | International Centre for Radio Astronomy Research
Midwife and signpost for photons
11.12.2017 | Julius-Maximilians-Universität Würzburg
Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.
To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...
The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.
Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...
With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong
Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...
An interdisciplinary group of researchers interfaced individual bacteria with a computer to build a hybrid bio-digital circuit - Study published in Nature Communications
Scientists at the Institute of Science and Technology Austria (IST Austria) have managed to control the behavior of individual bacteria by connecting them to a...
Physicists in the Laboratory for Attosecond Physics (run jointly by LMU Munich and the Max Planck Institute for Quantum Optics) have developed an attosecond electron microscope that allows them to visualize the dispersion of light in time and space, and observe the motions of electrons in atoms.
The most basic of all physical interactions in nature is that between light and matter. This interaction takes place in attosecond times (i.e. billionths of a...
11.12.2017 | Event News
08.12.2017 | Event News
07.12.2017 | Event News
12.12.2017 | Ecology, The Environment and Conservation
12.12.2017 | Ecology, The Environment and Conservation
12.12.2017 | Physics and Astronomy