Press Release 2013
The group of Xiao Hu (WPI-MANA PI), Qi-Feng Liang (MANA Research Associate) and Long-Hua Wu (NIMS Junior Researcher) has designed successfully a class of new topological materials, which, at the optimal condition, can transport zero-resistance edge current even above room temperature due to the large spin-orbit coupling. This quantized current is fully spin polarized and can be inverted by electric field, and therefore is useful for spintronics.
Topological insulator is a new quantum state realized by spin-orbit coupling. Its exploration has been the new frontier of condensed matter physics and material sciences recently. In a topological insulator, while insulating in the bulk, a sample possesses a quantum edge state which can transport dissipationless current, distinguishing itself from conventional insulators. Novel nano quantum functions of this new class of materials are explored. Unfortunately, it was realized only at very low temperature so far, and in the edge state spin-up and spin-down electrons are mixed, limiting its application.
Based on symmetry analysis and first-principles calculations, this group has discovered that one can achieve a new state called antiferromagnetic topological insulator by inserting a  mono-atomic layer of gold (Au) into a Mott insulator LaCrO3 of perovskite structure and applying an electric field along  direction. This theoretical work reveals a new direction for exploring topological materials and novel quantum functions.
The paper summarizing the new theory has been published in an open-access journal (Q. –F. Liang, L. –H. Wu and X. Hu, New Journal of Physics, vol.15, 063031, 2013). Patent has also been applied (12-MS-111SE).
Figure. Schematics for host perovskite material LaCrO3 in the  direction (blue slabs) with one atomic layer of La2Au2O6 (golden layer) inserted, where the Au atoms (golden balls) form a buckled honeycomb lattice.
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