Researchers' layered material brings spintronics closer to reality

February 19, 2017 // By Graham Prophet
All of the electronics we know today depends on representing information in terms of electric charge, and manipulating it by transport of that charge. A team of scientists from Munich and Kyoto report progress in the search to make the alternative – encoding information as electron spin – a realistic proposition. With a new layered material structure, information transport by spin is enabled at the interface between insulators.

Together with colleagues at the Kyoto University in Japan, scientists at the Walther-Meißner-Institute (WMI) and the Technical University of Munich (TUM) in Garching (Germany) have demonstrated the transport of spin information at room temperature in a remarkable material system, that creates a unique boundary layer system.


In their experiment, they demonstrated the production, transport and detection of electronic spins in the boundary layer between the materials lanthanum-aluminate (LaAlO 2) and strontium-titanate (SrTiO 3). What makes this material system unique is that an extremely thin, electrically conducting layer forms at the interface between the two non-conducting materials: a so-called two-dimensional electron gas.


The German-Japanese team has now shown that this two-dimensional electron gas transports not only charge, but also spin. “To achieve this we first had to surmount several technical hurdles,” says Dr Hans Hübl, scientist at the Chair for Technical Physics at TUM and Deputy Director of the Walther-Meißner-Institute. “The two key questions were: How can spin be transferred to the two-dimensional electron gas and how can the transport be proven?”


The scientists solved the problem of spin transfer using a magnetic contact. Microwave radiation forces its electrons into a precession movement, analogous to the wobbling motion of a top. Just as in a top, this motion does not last forever, but rather, weakens in time – in this case by imparting its spin onto the two-dimensional electron gas.


The electron gas then transports the spin information to a non-magnetic contact located one micron next to the contact. The non-magnetic contact detects the spin transport by absorbing the spin, building up an electric potential in the process. Measuring this potential allowed the researchers to systematically investigate the transport of spin and demonstrate the feasibility of bridging distances up to one hundred times larger than the distance of today’s transistors.


Based on these results, the team of scientists is now researching to what extent