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
New type of smart windows use liquid to switch from clear to reflective
14.12.2017 | The Optical Society
New ultra-thin diamond membrane is a radiobiologist's best friend
14.12.2017 | American Institute of Physics
MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.
Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...
Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...
Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.
To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...
The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.
Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...
With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong
Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...
11.12.2017 | Event News
08.12.2017 | Event News
07.12.2017 | Event News
14.12.2017 | Health and Medicine
14.12.2017 | Physics and Astronomy
14.12.2017 | Life Sciences