Posted: Sep 26, 2013 
Study reveals possibility of a quantum material to transport zeroresistance current above room temperature

(Nanowerk News) The group of Xiao Hu, QiFeng Liang and LongHua Wu has designed successfully a class of new topological materials, which, at the optimal condition, can transport zeroresistance edge current even above room temperature due to the large spinorbit coupling. This quantized current is fully spin polarized and can be inverted by electric field, and therefore is useful for spintronics ("Electrically tunable topological state in [111] perovskite materials with an antiferromagnetic exchange field ").


Schematics for host perovskite material LaCrO3 in the [111] direction (blue slabs) with one atomic layer of La2Au2O6 (golden layer) inserted, where the Au atoms (golden balls) form a buckled honeycomb lattice.

Topological insulator is a new quantum state realized by spinorbit 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 spinup and spindown electrons are mixed, limiting its application.

Based on symmetry analysis and firstprinciples calculations, this group has discovered that one can achieve a new state called antiferromagnetic topological insulator by inserting a [111] monoatomic layer of gold (Au) into a Mott insulator LaCrO3 of perovskite structure and applying an electric field along [111] direction. This theoretical work reveals a new direction for exploring topological materials and novel quantum functions.
