Study: Electrical Properties of Topological Insulators

SeaDiscovery.com
Monday, February 24, 2014
The NRL research team, left to right: Dr. Berend Jonker, Dr. Jeremy Robinson, Dr. Connie Li, and Dr. Olaf van't Erve. (Image: U.S. Naval Research Laboratory)

By Donna McKinney

Scientists at the U.S. Naval Research Laboratory (NRL) have demonstrated for the first time that one can electrically access the remarkable properties predicted for a topological insulator (TI). They used a ferromagnetic metal/tunnel barrier contact as a voltage probe to detect the spin polarization created in the topologically protected surface states when an unpolarized bias current is applied. This accomplishment identifies a successful electrical approach that provides direct access to the TI surface state spin system, significantly advances our fundamental understanding of this new quantum state, and enables utilization of the remarkable properties these materials offer for future technological applications. The results of this research have been published in Nature Nanotechnology (see http://www.nature.com/nnano/index.html and the digital object identifier 10.1038/nnano.2014.16).

Topological insulators constitute a new quantum phase of matter distinct from the classic dichotomy of simple metals and semiconductors. This phase was predicted in 2007 to exist in certain materials with high spin-orbit interaction, and confirmed a year later by spectroscopic measurements. While the bulk of a TI material is nominally an insulator, the surface layer (approximately one nanometer thick) is occupied by metallic states that are topologically protected from perturbations to their environment. TIs are expected to exhibit new behaviors and open horizons for science previously inaccessible with "conventional" materials. One of the most striking properties is that of spin-momentum locking—the spin of an electron in the TI surface state is locked at a right angle to its momentum. This consequently implies that when an unpolarized charge current flows in the topologically protected surface states, a net electron spin polarization should spontaneously appear whose amplitude and orientation are controlled by the charge current. This remarkable property has been anticipated by theory since 2010, but never measured by a transport experiment. Detecting this spin polarization directly as a voltage is key to understanding the fundamental properties of such materials, and interfacing them to electronic circuitry for future device applications.

The NRL team showed that a bias current indeed creates a net surface state spin polarization via spin-momentum locking in thin Bi2Se3 epitaxial films, and that this polarization was directly manifested as a voltage on a ferromagnetic metal contact. This voltage is proportional to the projection of the TI spin polarization onto the contact magnetization, is determined by the direction and magnitude of the bias current, and its sign is that expected from spin-momentum locking rather than a Rashba effect. Similar data are obtained for two different ferromagnetic tunnel barrier structures, Fe/Al2O3 and Co/MgO/graphene, demonstrating that these behaviors are independent of the details of the ferromagnetic contact.

This accomplishment offers a unique mechanism to generate and control spin in topological insulators, and may be useful for information processing. The International Technology Roadmap for Semiconductors, for example, has identified spin as a viable alternate state variable that should be developed for use in advanced electronic systems to complement the functionality provided by charge. The potential applications would certainly be long-term, because so little is known at this point, explains NRL's Dr. Berry Jonker. The existence of this new quantum phase of matter was just confirmed in 2008 and its properties yet to be fully understood, so it is a bit difficult to speculate on applications. But potential application areas include reconfigurable electronics, spintronics and quantum information processing.

The research team consists of Drs. Connie Li, Olaf van 't Erve, and Berend Jonker from NRL's Materials Science and Technology Division; Dr. Jeremy Robinson from NRL's Electronics Science and Technology Division; and Dr. Ying Liu and Prof. Lian Li from the University of Wisconsin, Milwaukee.

nrl.navy.mil
 

Maritime Reporter August 2014 Digital Edition
FREE Maritime Reporter Subscription
Latest Maritime News    rss feeds

Technology

BMT Nigel Gee To Launch Project L3 at Monaco Yacht Show

BMT Nigel Gee, a subsidiary of the BMT Group, will be launching its latest innovative design, ‘Project L3’ at the Monaco Yacht Show. Building on Nigel Gee’s

Dun & Bradstreet Partners Oracle to Reach for Cloud Solutions

Oracle and Dun & Bradstree, the world's leading source of commercial information and insight on businesses, today announced they have partnered to extend Oracle's

Aberdeen Harbour Installs Siklu Security Network

Aberdeen Harbour has extended its security solutions coverage using high-capacity backhaul from Siklu, the market leader in millimeter wave backhaul informs the Israel-based tech firm.

News

BMT Nigel Gee To Launch Project L3 at Monaco Yacht Show

BMT Nigel Gee, a subsidiary of the BMT Group, will be launching its latest innovative design, ‘Project L3’ at the Monaco Yacht Show. Building on Nigel Gee’s

Naming of M/V “SITC SHANDONG” at CSBC Shipyard

The Naming Ceremony of M/V “SITC SHANDONG” was held yesterday in Keelung Factory of CSBC Corporation, Taiwan, by SITC International Holdings Co., Ltd. (SITC International) and CSBC Corporation,

Hiab's State-of-the-art Factory Opens in Poland

Hiab, part of Cargotec, celebrates today the official opening of its new state-of-the-art multi-assembly unit (MAU) in Stargard Szczecinski, Poland. The development

Marine Science

BMT Nigel Gee To Launch Project L3 at Monaco Yacht Show

BMT Nigel Gee, a subsidiary of the BMT Group, will be launching its latest innovative design, ‘Project L3’ at the Monaco Yacht Show. Building on Nigel Gee’s

NOAA Orders Newbuild Navigation Response Boats

NOAA today announced that Lake Assault Boats of Superior, Wisconsin, will build two small vessels for the Office of Coast Survey's navigation response program,

Significant Progress on Perth Wave Energy Project

Wave energy developer Carnegie Wave Energy Limited has provided an update on the recent progress of the Perth Wave Energy Project. Carnegie has made significant

Electronics

Dun & Bradstreet Partners Oracle to Reach for Cloud Solutions

Oracle and Dun & Bradstree, the world's leading source of commercial information and insight on businesses, today announced they have partnered to extend Oracle's

Lilaas Engages Imtra for North American Distribution

Prospects in the North American marine equipment market have triggered a new and distribution agreement between control specialist Lilaas AS and marine and offshore

AN/SPY-1 SSSA Completes Critical Design Review

The Critical Design Review (CDR) stage for AN/SPY-1 radar Solid-State Switch Assembly (SSSA)'s high voltage modulator completed Aug. 26, confirming that the

 
 
Maritime Security Maritime Standards Naval Architecture Pod Propulsion Port Authority Ship Electronics Ship Repair Ship Simulators Sonar Winch
rss | archive | history | articles | privacy | terms and conditions | contributors | top maritime news | about us | copyright | maritime magazines
maritime security news | shipbuilding news | maritime industry | shipping news | maritime reporting | workboats news | ship design | maritime business

Time taken: 0.2110 sec (5 req/sec)