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
Unconventional superconductor may be used to create quantum computers of the future
19.02.2018 | Chalmers University of Technology
Hubble sees Neptune's mysterious shrinking storm
16.02.2018 | NASA/Goddard Space Flight Center
For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.
In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...
Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...
For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.
But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...
Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.
The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...
Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters
Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...
15.02.2018 | Event News
13.02.2018 | Event News
12.02.2018 | Event News
19.02.2018 | Materials Sciences
19.02.2018 | Materials Sciences
19.02.2018 | Life Sciences