14:30-15:10Plenary: Christopher PalmstromIntegration of Heusler Compounds with III-V Semiconductors: Semiconductor Spintronics & More
Heusler alloys are analogous to the Perovskite complex oxides with over 1000 possible combinations of elements. Their properties depend on the number of valence electrons per formula unit and have been predicted to be semiconductors, metals, ferromagnets, antiferromagnets, half metals, superconductors and topological insulators. Similar to compound semiconductors, the band structure and lattice parameters of Heusler alloys can also be tuned through alloying but over a much larger range of properties. The half-Heusler compounds can be thought of as a zincblende lattice with additional atoms in the octahedral sites. The lattice parameters and FCC crystal structure make them excellent candidates for integrating with conventional III-V semiconductors. Magnetic tunnel junctions using Heusler alloys that are predicted to be half metals have shown record tunneling magnetoresistance. We have demonstrated record high spin accumulation at Heusler/GaAs interfaces in lateral spin transport device structures and also the growth of semiconducting half-Heusler alloys on III-V semiconductors with comparable electron mobilities to Si. This presentation will emphasize Heusler compound integration on III-V semiconductors by molecular beam epitaxy and the tuning of their properties. 15:10-15:50Plenary: Qi-Kun XueQuantized Anomalous Hall Effect in Magnetically Doped Topological Insulators
Anomalous Hall effect (AHE) was discovered by Edwin Hall in 1881. In this talk, we report the experimental observation of the quantized version of AHE, the quantum anomalous Hall (QAH) effect in thin films of Cr-doped (Bi,Sb)2Te3 magnetic topological insulator on SrTiO3 substrate prepared by molecular beam epitaxy. The Cr0.15(Bi0.1Sb0.9)1.85Te3 films with a thickness of 5 nm exhibits ferromagnetic ordering at 15K. It was found that at zero magnetic field and 30 mK, the gate-tuned anomalous Hall resistance of the film is fully quantized at h/e2 accompanied by a significant drop of the longitudinal resistance. The longitudinal resistance vanishes under a strong magnetic field whereas the Hall resistance remains at the quantized value. The realization of the QAH effect paves a way for developing low-power-consumption electronics and spintronics.