[Keio Spintronics Network - Ohno Laboratory , Tohoku University]
In the Laboratory for Nanoelectronics and Spintronics at Tohoku Universitys Research Institute of Electrical Communication, Hideo Ohnos group is working to interpret the quantum mechanical aspects of spintronics and find applications for them. Many of the semiconductor devices used in current electronics are nonmagnetic, and show little effect as magnets. But in non-magnetic semiconductors, the quantum effects of spin become prominent. The researchers aim to control these effects, and utilize them to develop new forms of IT and quantum computers.
Q. With semiconductors, its usual to make integrated circuits. But what our group is doing is to turn semiconductors into magnets, and utilize electrical effects and spin effects in the semiconductors together. Theres no need for the materials to be semiconductors, but were using them to seek a new paradigm: controlling electrical effects using magnets, and controlling magnetic effects using electrical systems.
The spin in nonmagnetic semiconductors, especially the nuclear spin, is known to maintain the quantum mechanical phase coherence for a long time. In Hideo Ohnos group, Associate Professor Yuzo Ohno is detecting the quantum mechanical aspects of spin in semiconductors through highly sensitive methods using light. These methods are called transmission time-resolved pump-probe and time-resolved Faraday and Kerr rotation. In this way, Yuzo Ohno works to understand the spin-dependent properties of the materials and find applications for them.
Q. Spin is a quantum-mechanical physical property. If such quantum-mechanical states can be maintained for a long time, the up and down directions of spin can be used as 1 and 0 in computers. Theres also a state where the 1 and 0 states are superposed. If such states can be used as resources, then we hope that, for example, we can apply them in devices that form the basis for new forms of IT, such as quantum computing or quantum communication.
Spintronics technology is expected to lead to next-semiconductor devices that use quantum information. Many young researchers have sensed potential in spintronics, and are taking part in this R&D.
Q. Whereas a flow of electrical charge is called a electrical current, a flow of electron spin is called a spin current. This has become topical recently. Although the concept of spin current is still new, if it can be utilized, we hope that devices with entirely new functions will become possible.
Q. When you shine circular polarized laser light in a non-magnetic semiconductor, this generates electrons with their spins aligned. Then an interaction between the electron spins and nuclear spins align the nuclear spins at high degrees of the polarization. The orientations of the aligned nuclear spins can be changed freely, by instantaneously applying a magnetic field from outside. Moreover, the nuclear spins act on the electron spins as an effective magnetic field, which changes the precession of electron spins. This enables us to detect nuclear spin states, with high sensitivity, through electron spins.
Professor Hideo Ohno considers that progress in science and technology depends not only on results, but also on growth of the young researchers who will support future development.
Q. We offer not just research, but also training. The word training suggests deliberately making something, but here, training means that you become a member of the group, which includes students, postdocs, and staff. While working in a friendly team, our students get to truly understand what it means to do world-class research in science and technology. This process trains people to work together, and also to compete while coordinating with each other. I really hope people will understand and support the way that training works in this kind of environment.
Негізгі бет Ғылым және технология Quantum mechanical coherence of electron and nuclear spins in semiconductor electrons
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