Recently, Wei Han’s group, from the International Center for Quantum Materials (ICQM), demonstrated the spin injection and observation of inverse Edelstein effect in the Rashba-split 2DEG between SrTiO3 and LaAlO3 at room temperature. This work is cooperated with Jirong Sun’s group from institute of physics, Chinese academy of science. That is the first time to observe the inverse Edelstein effect generated spin signal in the 2DEG between two insulating oxides SrTiO3 and LaAlO3 up to room temperature. The work was reported by Science Advances with the title of “Observation of Inverse Edelstein Effect in Rashba-Split 2DEG between SrTiO3 and LaAlO3 at Room Temperature ”.
In 1990, Edelstein predicted that spin current could be induced by charge current flowing in inversion asymmetric two-dimensional electron gases (2DEGs), which is often referred to as the Edelstein effect (EE). The magnitude of EE highly depends on the Rashba spin-orbit coupling, which provides a locking between the momentum and spin polarization directions, as illustrated in fig (a). The opposite of EE is often called inverse Edelstein effect (IEE), which means that spin accumulation in inversion asymmetric 2DEG could generate an in-plane electric field perpendicular to the spin polarization direction. Because of the potential highly efficient spin-and-charge conversion, both the EE and IEE have attracted a great deal of interest for spintronics, and various experiments have been performed on the Rashba interfaces between two metallic films, two-dimensional materials, and the topological surface states.
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Figure. Observation of inverse Edelstein effect (IEE) in Rashba-split 2DEG between SrTiO3 and LaAlO3 at room temperature. A, The energy dispersion for a typical Rashba spin-split 2DEG. B, Schematic drawing of the IEE measurements. C. The gate voltage dependence of IEE of the Rashba-split 2DEG between 3 UC LaAlO3 and SrTiO3 at room temperature. Credit: International Center for Quantum Materials, Peking University.
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With the high-quality LAO/STO samples provided by the group of Jirong Sun, Wei Han’s group uses the spin pumping technique to inject the spin current from Py electrode through a LaAlO3 layer with a thickness of up to 40 unit cells into the 2DEG at the junction interface and measured the inverse Edelstein effect at the room temperature, as illustrated in the figure (b). Systematical measurements, including frequency, power, temperature and LAO thickness dependences of the spin signal strongly support the observation. As shown in figure(c), The gate voltage dependence of the spin signal indicate the gate voltage a powerful tool to turn the spin-to-charge conversion efficiency and even to turn the signal on/off.
This work has been published on Science Advances on March 17, 2017 (Science Advances, 3, e1602312 (2017)). PhD student Qi Song from ICQM and Hongrui Zhang from IOP are the co-first authors of this paper. This work was supported by National Basic Research Programs of China, National Natural Science Foundation of China, the Strategic Priority Research Program of the Chinese Academy of Sciences, Recruitment Program of Global Experts, CAS Hundred Talent Program, the DOE BES Award, the support by the 1000 Talents Program for Young Scientists of China.
Besides, it is worth to mention that the France team led by Prof. Albert Fert, 2007 Nobel Laureate in physics, also did a work on the spin and charge conversion at the oxide interface. Their work is published in Nature Materials (Nature Materials 15, 1261–1266 (2016)), which is a little earlier than the work discussed above.
Both these two work reveal that the oxide interface could be used for spintronics devices, such as efficient charge-to-spin conversion for the generation and detection of spin current.
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