Spin current detected at room temperature, says team

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Researchers at Chalmers University of Technology say they have used a ferromagnetic detector to sense spin current on topological insulator surfaces at room temperature.

The team detected the surface spin current on bismuth selenide (Bi2Se3) using ferromagnetic tunnel contacts. These contacts, known to be very sensitive to spin polarisation, probe the Bi2Se3 surface by measuring the magnetoresistance due to parallel and anti-parallel alignment of the spin current and the ferromagnet magnetisation direction.

“The key factors for these room temperature results are good quality topological insulator crystals and spin sensitive ferromagnetic tunnel contacts carefully prepared by clean room nanofabrication”, said Dr André Dankert.

Topological insulators are insulators inside the bulk, but conduct on their surfaces with less resistance than the conventional materials. This is possible due to their uniquely strong interaction between electrons’ spin and orbital angular momentum with their time reversal symmetry. The interaction is so strong that the spin angular momentum of the electrons is locked perpendicular to their momentum and generates a spontaneous spin polarised current on the surfaces of topological insulators by applying an electric field.

“Our results show the electrical accessibility of spin currents on topological insulator surfaces up to room temperature and pave the way for further developments, which can be useful for spin based information processing in the future”, says associate professor Saroj Dash, who leads the research group.

However, Dash cautions the research is still in its early stage and more experiments are required for further understanding.