Collision experiments in semiconductors come into reach
Our standard model of the smallest bits of matter rests upon evidence gathered from particle accelerators and collider experiments. A team of physicists from Regensburg (Germany), Marburg (Germany), and Santa Barbara (USA) have now realized a collider for particles in solids. This fundamentally new concept will be reported in the upcoming issue of Nature.
Already little children tend to smash all sorts of things together to learn about their interactions and properties. Particle colliders apply this natural idea to study the building blocks of matter. In the early 1900’s, Ernest Rutherford shot α-particles onto gold foils and concluded from their scattering properties that atoms contain their mass in a very small nucleus. A hundred years later, the greatest collaboration in modern science smashed protons into each other in the pursuit and discovery of the Higgs boson.
Such an elemental collider concept is absent in solid-state research, although our modern technology crucially depends on knowing the structural and electronic properties of solids. In a crystal, the complex interaction of the billions upon billions of particles boils down to simple entities, so-called quasiparticles. However, it is extremely difficult to single out specific quasiparticles among a large ensemble of them.
A team of physicists from Germany and the US have now succeeded in smashing such elementary excitations of a solid into each other. Since the quasiparticles only exist for a flash of time, it was crucial to operate on ultrashort timescales. If one second was compared to the age of the universe, a quasiparticle would exist only for a few hours.
The scientists used a unique laser source (terahertz high-field lab, Regensburg) to produce hard evidence on collisions within excitons, which are pairs of electrons and holes (electron vacancies) bound by the attractive Coulomb-force between them, in a thin crystal of tungsten diselenide. A femtosecond optical pulse (1 femtosecond equals a millionth of a billionth of a second) creates excitons at a precise time with respect to an intense light pulse in the terahertz spectral regime (1 terahertz means one trillion oscillations per second).
The lightwave of the terahertz pulse accelerates the constituents of the exciton, i.e. electrons and holes, within a period shorter than a single oscillation of light. The experiment shows that only excitons created at the right time lead to electron–hole collisions, just as in conventional synchrotron accelerators. This re-collision generates ultrashort light bursts encoding key aspects of the solid. The observations in the laboratory are supported and explained by a quantum mechanical simulation carried out by physicists from the University of Marburg.
These time-resolved collision experiments in a solid prove that basic collider concepts can be utilized to transfer versatile methods from particle physics to solid-state research and shed new light on quasiparticles and many-body excitations in condensed matter systems. Ultimately, this approach might lead to the clarification of some of the most outstanding enigmas of condensed matter physics such as the binding mechanism of Cooper pairs in high temperature superconductors.
F. Langer, M. Hohenleutner, C. Schmid, C. Poellmann, P. Nagler, T. Korn, C. Schüller, M. S. Sherwin, U. Huttner, J. T. Steiner, S. W. Koch, M. Kira, and R. Huber, Lightwave-driven quasiparticle collisions on a sub-cycle timescale, Nature 2016
Publication: doi 10.1038/nature17958
Prof. Dr. Rupert Huber
Prof. Dr. Mackillo Kira
Alexander Schlaak | idw - Informationsdienst Wissenschaft
A tale of two pulsars' tails: Plumes offer geometry lessons to astronomers
18.01.2017 | Penn State
Studying fundamental particles in materials
17.01.2017 | Max-Planck-Institut für Struktur und Dynamik der Materie
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
18.01.2017 | Power and Electrical Engineering
18.01.2017 | Materials Sciences
18.01.2017 | Life Sciences