Ultrafast snapshots of relaxing electrons in solids


MPQ, FG Attoelectronics

Attosecond flashes of light and x-rays take snapshots of fleeting electrons in solids.

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole behind. For a long time, scientists have suspected that the liberated electron and the positively charged hole form a new kind of quasiparticle — known as ‘core-exciton’. But so far, there has not yet been a real proof of its existence. Scientists have a wide range of tools to track excitons in semiconductors in real-time. Those are generated by ordinary light, and can be employed in various applications in optoelectronics and microelectronics. On the contrary, core-excitons are extremely short-lived, and up to now, no technique was available to track their motion and deduce their properties.

A team of scientists led by Dr. Eleftherios Goulielmakis, head of the research group “Attoelectronics” at the Max Planck Institute of Quantum Optics, have been able to capture the dynamics of core-excitons in solids in real-time. Using flashes of x-ray radiation lasting only few hundred attoseconds followed by optical light flashes of similar duration (a tool developed by the group last year) the scientists obtain an ultrafast camera which allowed them to take snapshots of the short-lived excitons in silicon dioxide for the first time.

“Core-excitons live for a very short time because their interactions with other particles in the solid quickly stops their motion,” said Antoine Moulet, leading author in this work. “In quantum mechanics we say that the exciton loses its coherence,” he adds.

A key tool to track the dynamics of core-excitons has been the development of attosecond light flashes in the optical range. The work was published by the Attoelectronics group last year.

“In our experiment we use x-ray flashes to light up core-excitons in solids, whereas the optical attosecond pulses provide the possibility to resolve this motion in real-time,” says Julien Bertrand, a former researcher in the group of Goulielmakis, at present assistant professor at Laval University, Canada. “The combination of both allowed us to take snapshots of the motion of core-excitons which lived for approximately 750 attoseconds.”

But the study was not limited to capturing these fleeting motions inside solids. “We were able to acquire quantitative information about the properties of core-excitons such as their miniature dimension which were merely bigger than that of a single atom, or how easily they are polarized by visible light,” says Goulielmakis. “Our technique advances excitonics, i.e. the measurement, the control and the application of excitons in the x-ray regime. But at the same time, it is a general tool for studying ultrafast x-ray initiated processes in solids on their natural time scales. Such a capability has never before been possible in x-ray science.”

The team now envisages applications of their technique for studying ultrafast processes at interfaces of solids, and new routes to realize ultrafast switches for x-ray radiation based on optical light fields. “With x-ray free electron lasers rapidly proliferating around the world, the capability of controlling x-rays with visible light becomes increasingly important,” says Goulielmakis.

Facts, background information, dossiers
  • electrons
  • MPI für Quantenoptik
  • X-rays
  • quasiparticles
  • excitons
  • real-time imaging
  • silicon dioxide
  • quantum mechanics
More about MPI für Quantenoptik
  • News

    Mapping electromagnetic waveforms

    Temporally varying electromagnetic fields are the driving force behind the whole of electronics. Their polarities can change at mind-bogglingly fast rates, and it is difficult to capture them in action. However, a better understanding of the dynamics of field variation in electronic compone ... more

    A signal boost for molecular microscopy

    Carbon nanotubes can be produced with a variety of shapes and properties and are therefore of much interest for widespread applications in fields as diverse as electronics, photonics, nanomechanics, and quantum optics. Hence it is important to have a tool at hand that allows to determine th ... more

    Attosecond camera for nanostructures

    Physicists of the Laboratory for Attosecond Physics at the Max Planck Institute of Quantum Optics and the Ludwig-Maximilians-Universität Munich in collaboration with scientists from the Friedrich-Alexander-Universität Erlangen-Nürnberg have observed a light-matter phenomenon in nano-optics, ... more

More about Max-Planck-Gesellschaft
  • News

    Molecular Force Sensors

    Proteins are often considered as molecular machines. To understand how they work, it is not enough to visualize the involved proteins under the microscope. Wherever machines are at work mechanical forces occur, which in turn influence biological processes. These extremely small intracellula ... more

    The proton precisely weighted

    What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the ... more

    10-fold speed up for the reconstruction of neuronal networks

    Scientists working in „connectomics“, a research field occupied with the reconstruction of neuronal networks in the brain, are aiming at completely mapping of the millions or billions of neurons found in mammalian brains. In spite of impressive advances in electron microscopy, the key bottl ... more

Your browser is not current. Microsoft Internet Explorer 6.0 does not support some functions on Chemie.DE