To process and save data more and more quickly, to build even smaller and more powerful chips: these are the goals pursued by numerous research teams around the world.
For some years now, one special material class has been at the heart of their efforts, so-called topological insulators. Within these, electrons automatically separate according to their respective spin orientation, entirely without the use of electric or magnetic fields.
“This property is of far-reaching significance,” explains Professor Ralph Claessen from the Institute of Physics at the University of Würzburg: “If you apply electrical contacts to topological insulators, you can build circuits that transmit information coded with the spin orientation.” This new data transmission method is no longer based on the transport of electrical charges. It is therefore much faster and more reliable.
Why tin represents progress
Würzburg physicists have now, for the first time, succeeded in creating topological insulators made from tin, a simple and readily available material. “This makes production much easier because insulators like these have only ever been made from complex chemical compounds or hazardous materials,” says Claessen’s colleague Jörg Schäfer.
The physicists are presenting their findings in the journal “Physical Review Letters”. They have achieved their success as part of an international collaboration with teams from Switzerland and the USA as well as from the Jülich Research Center. At Würzburg’s Institute of Physics, Professor Laurens Molenkamp also works with topological insulators, and successfully so: a few years ago, motivated by theoretical predictions, he became the first person to verify the unusual properties of this material class in a series of experiments.
How the topological insulator came about
In the new experiments under Ralph Claessen’s chairmanship and Jörg Schäfer’s leadership, thin layers of tin were vapor-deposited onto a semiconductor substrate extremely slowly. An orderly crystal lattice of tin atoms formed, identical to that of diamond.
“Experiments then revealed that this layer has the unusual properties we were looking for: the spins of the electrons are sorted into two directions with opposite magnetic needle orientation, and the two groups move in opposite directions,” says Schäfer. This was proven with spin-resolved photoemission.
“This has enabled us to show, for the very first time, that the phenomenon of automatic spin separation also exists in a simple, elementary crystal lattice,” enthuses Schäfer. As a result, he believes that the production of practical topological insulators is now tantalizingly close. The new experiments were underpinned by theoretical observations that Würzburg physics professor Werner Hanke made with colleagues in Jülich.
Next steps for the physicists
Since the spin separation in the tin lattice itself can now be reliably produced, the physicists next want to explore and optimize the conductive behavior of complete structures with electrical contacts.
Initial demonstrations of spin transport in layers with topological materials have already worked at temperatures well below freezing. So, for practical application, a number of technological issues still need to be clarified, including the realization of circuits that work without cooling. For this purpose, the Würzburg physicists are now working intensively together, pooling their expertise in material production and analysis.
“Elemental Topological Insulator with Tunable Fermi Level: Strained alpha-Sn on InSb(001)”, A. Barfuss, L. Dudy, M. R. Scholz, H. Roth, P. Höpfner, C. Blumenstein, G. Landolt, J. H. Dil, N. C. Plumb, M. Radovic, A. Bostwick, E. Rotenberg, A. Fleszar, G. Bihlmayer, D. Wortmann, G. Li, W. Hanke, R. Claessen, and J. Schäfer, Physical Review Letters 111, 157205 (October 2013), DOI: 10.1103/PhysRevLett.111.157205
Dr. Jörg Schäfer, Institute of Physics, University of Würzburg, firstname.lastname@example.org
Robert Emmerich | Source: Uni Würzburg
Further information: www.uni-wuerzburg.de
More articles from Physics and Astronomy:
Supernova Blast Provides Clues to Age of Binary Star System
05.12.2013 | Chandra X-ray Center
Glimpsing the Infrastructure of a Gamma-ray Burst Jet
05.12.2013 | NASA/Goddard Space Flight Center
The Light: Global study gets underway with online user survey
Light has a fundamental impact on our sense of well-being and performance. In cooperation with Zumtobel, a supplier of lighting solutions, Fraunhofer IAO has launched a global user survey of lighting quality in offices. The objective is to identify the best lighting conditions for a variety of spaces and lighting ...
Quantum entanglement, a perplexing phenomenon of quantum mechanics that Albert Einstein once referred to as “spooky action at a distance,” could be even spookier than Einstein perceived.
Physicists at the University of Washington and Stony Brook University in New York believe the phenomenon might be intrinsically linked with wormholes, hypothetical features of space-time that in popular science fiction can provide a much-faster-than-light shortcut from one part of the universe to another.
But here’s the catch: One couldn’t actually ...
A star is formed when a large cloud of gas and dust condenses and eventually becomes so dense that it collapses into a ball of gas, where the pressure heats the matter, creating a glowing gas ball – a star is born.
New research from the Niels Bohr Institute, among others, shows that a young, newly formed star in the Milky Way had such an explosive growth, that it was initially about 100 times brighter than it is now. The results are published in the scientific journal, Astrophysical Journal Letters.
The young ...
EPFL scientists have shown how to achieve a dramatic increase in the capacity of optical fibers; Their simple, innovative solution reduces the amount of space required between the pulses of light that transport data
Optical fibers carry data in the form of pulses of light over distances of thousands of miles at amazing speeds. They are one of the glories of modern telecommunications technology.
However, their capacity is limited, because the pulses of light need to be lined up one after the other in ...
NASA's Hurricane and Severe Storms Sentinel airborne mission known as HS3 wrapped up for the 2013 Atlantic Ocean hurricane season at the end of September, and had several highlights. HS3 will return to NASA’s Wallops Flight Facility in Wallops Island, Va., for the 2014 Atlantic hurricane season.
During the 2013 mission, two unmanned Global Hawks flew from Wallops for the first time. The mission highlights included studying the Saharan Air Layer, following the genesis of a tropical storm, finding a unique hybrid core or center circulation in a redeveloped storm, obtaining measurements on the strongest side of ...
05.12.2013 | Health and Medicine
05.12.2013 | Ecology, The Environment and Conservation
05.12.2013 | Information Technology
05.12.2013 | Event News
04.12.2013 | Event News
12.11.2013 | Event News