Scientists from the Swiss Nanoscience Institute and the Department of Physics at the University of Basel have demonstrated for the first time how electrons are transported from a superconductor through a quantum dot into a metal with normal conductivity. This transport process through a quantum dot had already been calculated theoretically in the nineties, but scientists at the University of Basel have now succeeded in proving the theory with measurements. They report on their findings in the scientific journal “Physical Review Letters”.
Transport properties such as electrical conductivity play an important role in technical applications of new materials and electronic components. Completely new phenomena occur, for example, when you combine a superconductor and nanometer-sized structures, known as quantum dots, in a component.
Researchers at the University of Basel working under Professor Christian Schönenberger have now constructed such a quantum dot between a superconductor and a metal with normal conductivity to study electron transport between the two components.
It should in fact be impossible to transport electrons from the superconductor through a quantum dot at low energies. Firstly, electrons never occur on an individual basis in a superconductor but rather always in two's or in so-called Cooper pairs, which can only be separated by relatively large amounts of energy. Secondly, the quantum dot is so small that only one particle is transported at a time due to the repulsive force between electrons.
In the past, however, scientists have repeatedly observed that a current nonetheless runs between the superconductor and the metal – in other words, electron transport does occur through the quantum dot.
First evidence of the transport mechanism through a quantum dot
On the basis of quantum mechanics, theories were developed in the nineties which indicated that the transport of Cooper pairs through a quantum dot is entirely possible under certain conditions. The prerequisite is that the second electron follows the first very quickly, namely within the time roughly stipulated by Heisenberg's uncertainty principle.
The scientists at the University of Basel have now been able to accurately measure this phenomenon. In their experiments the scientists found the exact same discrete resonances that had been calculated theoretically. In addition, the team including doctoral student Jörg Gramich and his supervisor Dr. Andreas Baumgartner was able to provide evidence that the process also works when energy is emitted into the environment or absorbed from it.
“Our results contribute to a better understanding of the transport properties of superconducting electronic nanostructures, which are of great interest for quantum technology applications”, says Dr. Andreas Baumgartner.
J. Gramich, A. Baumgartner, and C. Schönenberger
Resonant and inelastic Andreev tunneling observed on a carbon nanotube quantum dot
Physical Review Letters 115, doi: 10.1103/PhysRevLett.115.216801
Dr. Andreas Baumgartner, University of Basel, Department of Physics, tel. +41 61 267 39 06, email: email@example.com
Reto Caluori | Universität Basel
Thin films from Braunschweig on the way to Mercury
19.10.2018 | Fraunhofer-Institut für Schicht- und Oberflächentechnik IST
Extremely close look at electron advances frontiers in particle physics
19.10.2018 | National Science Foundation
Scientists at the Max Planck Institute for Polymer Research (MPI-P) in Mainz (Germany) together with scientists from Dresden, Leipzig, Sofia (Bulgaria) and Madrid (Spain) have now developed and characterized a novel, metal-organic material which displays electrical properties mimicking those of highly crystalline silicon. The material which can easily be fabricated at room temperature could serve as a replacement for expensive conventional inorganic materials used in optoelectronics.
Silicon, a so called semiconductor, is currently widely employed for the development of components such as solar cells, LEDs or computer chips. High purity...
Augsburg chemists present a new technology for compressing, storing and transporting highly volatile gases in porous frameworks/New prospects for gas-powered vehicles
Storage of highly volatile gases has always been a major technological challenge, not least for use in the automotive sector, for, for example, methane or...
When we put water in a freezer, water molecules crystallize and form ice. This change from one phase of matter to another is called a phase transition. While this transition, and countless others that occur in nature, typically takes place at the same fixed conditions, such as the freezing point, one can ask how it can be influenced in a controlled way.
We are all familiar with such control of the freezing transition, as it is an essential ingredient in the art of making a sorbet or a slushy. To make a cold...
Thin organic layers provide machines and equipment with new functions. They enable, for example, tiny energy recuperators. In future, these will be installed...
Das Zusammenspiel aus Struktur und Dynamik bestimmt die Funktion von Proteinen, den molekularen Werkzeugen der Zelle. Durch Fortschritte in der...
17.10.2018 | Event News
16.10.2018 | Event News
02.10.2018 | Event News
19.10.2018 | Life Sciences
19.10.2018 | Physics and Astronomy
19.10.2018 | Trade Fair News