Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New Technique: Physicists generate terahertz waves with spin current flow

01.02.2018

Terahertz waves are often used in the checking of passengers and luggage at the airport. They are also in demand in other areas, such as for materials testing in the industry. Physicists at the University of Kaiserslautern (TUK) have now developed a new method for generating such waves. They use a quantum magnetic current flow, so-called spin current, in magnetic metal nanostructures. The cost-effective and material-saving technology has the potential for industry applications. The study was published in the renowned scientific journal "Scientific Reports".

Terahertz (THz) waves lie in the electromagnetic spectrum between microwaves and infrared radiation. They are invisible to the human eye. Since they are low in energy, there is no need for be concerned with their impact on human.


Associate Professor Dr. Evangelos Papaioannou

Credit: TUK/Thomas Koziel


The diagram illustrates how the new technique works.

Credit: Papaioannou

Today, they play a role in medical and communications technology, but also in materials testing. For example, they were used to inspect the plastic insulation on space shuttle. However, powerful radiation sources, i.e. emitters, are needed to generate the waves. This is usually associated with high energy consumption and costs.

A very efficient and at the same time more cost-effective method has now been developed by Kaiserslautern researchers, in which they use a so-called spin current. This is analogous to the electric current, in which electrical charges, namely electrons, flow.

"A spin describes the intrinsic angular momentum of a quasiparticle, such as an electron," says Associate Professor Dr. Evangelos Papaioannou, who is a researcher with his own sub-group in the Magnetism Research Group lead by Professor Burkard Hillebrands in Department of Physics at TUK. "It forms the basis for all magnetic phenomena. Simply said, an electron rotates left or right around its axis like a spinning top."

A special nanostructure has been developed by the research team of Papaioannou for the application of the technique. "It consists of a metal bilayer of magnetic iron and non-magnetic platinum," as the physicist describes the structure. "These are very thin layers that are only a few nanometers thick."

To generate the terahertz waves, the researchers use a femtosecond laser that emits extremely short laser pulses. As a result, the following happens: "When the laser pulses hit the nanostructure they stimulate the electrons in the iron film, creating a spin current," says the Papaioannou. This current flows into the adjacent platinum layer. Here comes a certain physical phenomenon into play, the inverse Spin-Hall Effect. For platinum, this effect has been known for some time. It arises due to the atomic structure of the metal.

"The atomic nuclei of platinum deflect electrons with a left- and right-handed spin in opposite directions, which leads to the transformation of the spin current into an ultrafast transient charge current, which is then the source of terahertz waves”.

As a special feature of the experimental setup, a small silicon lens is attached to the structure. "We are bundling the waves", the Junior Professor continues. In this way, the terahertz waves could be forwarded easily and efficiently in future applications.

In their recently published paper, the researchers have revealed, among other things, how layer thicknesses and the arrangement of materials must be best designed to produce the THz waves. The research field of THz spintronics technology is an emerging field. Only recently, research colleagues in Berlin showed for the first time that terahertz waves can be generated by spin current.

The work of the Kaiserslautern researchers reveals now a way to optimize the emitters so that they can reach their maximum efficiency. This makes them cheaper and more interesting for various fields of application, for example for security techniques, materials testing and information technologies, but also for basic research.

The team of Papaioannou is a part of the State Research Center for Optics and Material Sciences (OPTIMAS), which is funded by the state of Rhineland-Palatinate. Professor R. Beigang and Dr. G. Torosyan also contributed to the study, both are experts in the field of Terahertz. The work was supported by the Deutsche Forschungsgemeinschaft within the scope of the Collaborative Research Center SPIN + X, as well as the Carl-Zeiss Foundation.

The study was published in the prestigious journal Scientific Reports: "Optimized Spintronic Terahertz Emitters Based on Epitaxial Grown Fe / Pt Layer Structures" DOI: 10.1038 / s41598-018-19432-9

Questions can be directed at:
Juniorprof. Dr. Evangelos Papaioannou
Tel.: +49(0)631 205-4099
E-Mail: papaio(at)rhrk.uni-kl.de

Melanie Löw | Technische Universität Kaiserslautern
Further information:
http://www.uni-kl.de

More articles from Physics and Astronomy:

nachricht From the cosmos to fusion plasmas, PPPL presents findings at global APS gathering
13.11.2018 | DOE/Princeton Plasma Physics Laboratory

nachricht A two-atom quantum duet
12.11.2018 | Institute for Basic Science

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

Im Focus: Coping with errors in the quantum age

Physicists at ETH Zurich demonstrate how errors that occur during the manipulation of quantum system can be monitored and corrected on the fly

The field of quantum computation has seen tremendous progress in recent years. Bit by bit, quantum devices start to challenge conventional computers, at least...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

European Space Talks: Weltraumschrott – eine Gefahr für die Gesellschaft?

23.10.2018 | Event News

 
Latest News

NIH scientists illuminate causes of hepatitis b virus-associated acute liver failure

14.11.2018 | Life Sciences

The unintended consequences of dams and reservoirs

14.11.2018 | Earth Sciences

NIH scientists combine technologies to view the retina in unprecedented detail

14.11.2018 | Medical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>