Atoms

  • A Nano-Roundabout for Light

    Functional principle of a nano-roundabout.  © TU Wien

    At TU Wien, it was possible to create a nanoscale optical element that regulates the flow of light particles at the intersection of two glass fibers like a roundabout. A single atom was used to control the light paths. Just like in normal road traffic, crossings are indispensable in optical signal processing. In order to avoid collisions, a clear traffic rule is required. A new method has now been developed at TU Wien to provide such a rule for light signals. For this purpose, the two glass fibers were coupled at their intersection point to an optical resonator, in which the light circulates and behaves as in a roundabout. The direction of circulation is defined by a single atom coupled to the resonator. The atom also ensures that the light always leaves the roundabout at the next exit. This rule is still valid even if the light consists merely of individual photons. Such a roundabout will consequently be installed in integrated optical chips – an important step for optical signal processing.

  • Electron highway inside crystal

    Step edges on topological crystalline insulators may lead to electrically conducting pathways where electrons with opposite spin spin move in converse directions - any U-turn is prohibited. Picture: Thomas Bathon/Paolo Sessi/Matthias Bode

    Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science. Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was highlighted again as the Royal Swedish Academy of Sciences in Stockholm awarded this year's Nobel Prize in Physics to three British scientists for their research of so-called topological phase transitions and topological phases of matter.

  • Kaiserslautern physicists observe diffusion of individual atoms in light bath

    First author Farina Kindermann and Professor Artur Widera in front of a quantum gas experi-mental setup for investigations on single atoms. University of Kaiserslautern/Thomas Koziel

    In a combination of experiments and theory the diffusion of individual atoms in periodic systems was understood for the first time. The interaction of individual atoms with light at ultralow temperatures close to the absolute zero temperature point provides new insights into ergodicity, the basic assumption of thermodynamics. Quantum physicists at University of Kaiserslautern have published their results together with colleagues in the renowned scientific journal “Nature Physics”.

  • Light-driven atomic rotations excite magnetic waves

    Light-driven atomic rotations (spirals) induce coherent motion of the electronic spins (blue arrows). Image: J.M. Harms/MPI for the Structure and Dynamics of Matter

    Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion. Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how the ultrafast light-induced modulation of the atomic positions in a material can control its magnetization. An international research team led by Andrea Cavalleri from the Max Planck Institute for the Structure and Dynamics of Matter at CFEL in Hamburg used terahertz light pulses to excite pairs of lattice vibrations in a magnetic crystal.

  • Matter-antimatter symmetry confirmed with precision record

    Sketch of the experimental setup used at CERN for the determination of the antiproton-to-electron mass ratio. Graphic: Masaki Hori

    CERN experiment sets precision record in the measurement of the antiproton to electron mass ratio using a new innovative cooling technique. According to the Standard Model of elementary particle physics, to each particle exists an antiparticle that is supposed to behave exactly the same way. Thus, “anti-people” in an “anti-world” would observe the same laws of physics, or make the same experiences in general, as we do. This postulate is, however, difficult to prove, since it is almost impossible to perform measurements on antimatter: whenever an antiparticle meets is matter-counterpart, both particles annihilate, accompanied by the creation of energy.

  • Molekül-Motoren mit Licht-Antrieb

    Bahnbrechende Entwicklung: Zwei Nano-Maschinen (weiß) auf einer 8x8 Nanometer großen Kupferoberfläche (grau), aufgenommen bei -267° mit einem Rastertunnelmikroskop. In Gelb die Molekül-Modelle der Maschinen. Foto: Uni Graz/Grill

    ForscherInnen der Uni Graz steuern Nano-Maschinen auf Oberflächen. Ferngesteuerte Nano-Maschinen, angetrieben von einem Lichtstrahl, reinigen Oberflächen, bringen spezielle Pharmazeutika im Körper an ihren Zielort oder bauen elektronische Strukturen aus einzelnen Atomen. Dieser Zukunftsvision ist die Arbeitsgruppe von Univ.-Prof. Dr. Leonhard Grill vom Institut für Chemie der Karl-Franzens-Universität Graz einen großen Schritt nähergekommen: Dem Team ist es gelungen, einzelne molekulare Maschinen durch Laserlicht gezielt auf einer Oberfläche zu bewegen und währenddessen zu beobachten. Die Ergebnisse der Studie werden in der nächsten Ausgabe des Magazins „ACS Nano“ publiziert und sind online bereits veröffentlicht.

  • New Quantum States for Better Quantum Memories

    An artificial diamond under the optical microscope. The diamond fluoresces because due to a number of nitrogen defects. TU Wien

    How can quantum information be stored as long as possible? An important step forward in the development of quantum memories has been achieved by a research team of TU Wien. Conventional memories used in today’s computers only differentiate between the bit values 0 and 1. In quantum physics, however, arbitrary superpositions of these two states are possible. Most of the ideas for new quantum technology devices rely on this “Superposition Principle”. One of the main challenges in using such states is that they are usually short-lived. Only for a short period of time can information be read out of quantum memories reliably, after that it is irrecoverable.

  • Observing the birth of a spectral line

    Absorption in a helium as it depends on the photon energy of the exciting extreme-ultraviolet flash of light and the time delay to the ionizing near-infrared laser pulse acting as a cut-off gate. graphics: MPIK

    Ultrashort intense laser pulses cut into a fundamental quantum phenomenon.
    For the first time, physicists managed to observe in real time how an atomic spectral line emerges within the incredibly short time span of a few femtoseconds, verifying a theoretical prediction. This has been possible by applying a very fast temporal switch: An intense laser pulse cuts off the natural decay shortly after excitation by a preceding laser pulse. The build-up of the asymmetric Fano line shape of two quantum-mechanically interfering electrons in the Helium atom is measured by varying the time delay between the two laser pulses.

  • Partnership at a distance: Deep-frozen helium molecules

    “When two loners are forced to share a bed, they move well beyond its edges to get away from each other.” Peter Evers

    As atomic physicists in Frankfurt have now been able to confirm, over 75 percent of the time helium atoms are so far apart that their bond can be explained only by the quantum-mechanical tunnel effect. Helium atoms are loners. Only if they are cooled down to an extremely low temperature do they form a very weakly bound molecule. In so doing, they can keep a tremendous distance from each other thanks to the quantum-mechanical tunnel effect. As atomic physicists in Frankfurt have now been able to confirm, over 75 percent of the time they are so far apart that their bond can be explained only by the quantum-mechanical tunnel effect.

  • Quantum Particles Form Droplets

    Quantum droplets may preserve their form in absence of external confinement because of quantum effects. IQOQI/Harald Ritsch

    In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

  • Speeding up electronics with light

    Light pulses generate Multi-PHz electric current in bulk solids. The emitted extreme ultraviolet radiation allows scientists to record these electric currents in real time. Graphic: Research Group Attoelectronics, MPQ

    By using ultrafast laser flashes, scientists at Max Planck Institute of Quantum Optics generated and measured the fastest electric current inside a solid material. The electrons executed eight million billion oscillations per second, setting a record of human control of electrons inside solids! The performance of modern electronic devices such as computers or mobile phones is dictated by the speed at which electric currents can be made to oscillate inside their electronic circuits.

  • Ultrafast slow-motion microscope sees a single molecule vibrate

    Single pentacen molecules vibrate on a gold surface. Foto: Dominik Peller

    An international team of scientists based in Regensburg, Germany, has now recorded the ultrafast motion of a single molecule directly in time and space by combining a femtosecond laser with an atomic resolution microscope. Atoms and molecules are the constituents of virtually all matter that surrounds us. Interacting with each other while following the rules of nature, they form complex systems ranging from modern technology to living creatures. Their behavior, that is, what they actually do, basically determines all of natural and life sciences. They are so small, however, that we cannot observe them in daily life.