Symmetry-protected spin dynamics in ferroelectric spin device

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Award Title:Symmetry-protected spin dynamics in ferroelectric spin device (Proposal ID: 2031692)Non-technical Abstract:To boost the computing power of microelectronic systems, among many strategies such as device miniaturization, using non-charge-based logic operation and harnessing non-von Neumann architectures, computing with electron spin has been proposed as a promising solution. Spin devices such as spin field effect transistor are considered to have the potential to significantly advance computing performance and even transform current computing paradigms. In spin devices, control of electron spin – a computing process – is achieved by electric field-induced effective magnetic field in the hosting semiconductor. In most semiconductors, the magnetic field is multi-directional so coherent control of electron spin precession has been a challenge. In this project, the PI will address this issue by developing material/device systems that provide unidirectional magnetic field. In the proposed system, electric field stems from ferroelectric polarization and unidirectional magnetic field is a natural consequence of the unique symmetry of the proposed system. The nonvolatile electric field and the unidirectional magnetic field will make the proposed spin devices excel in spin control and power consumption. This award supports the fundamental research of understanding symmetry-spin dynamics relation in ferroelectric spin devices. The basic knowledge obtained from this project would help the realization of technologically practical spin field effect transistors. The results from this award will therefore benefit the U.S. economy by advancing technological progresses in the field of microelectronics. The award will also promote engineering education and research training of underrepresented groups. Technical Abstract:The research objective of this project is to understand the role of symmetry and the persistent spin helix on the spin dynamics in ferroelectric semiconductors with strong spin-orbit coupling for spintronic devices. While strong spin-orbit coupling enhances spin precession leading to short channel operation, it also simultaneously suppresses controllable spin transport. Such dilemma has been a major roadblock for realization of practical spintronic devices such as spin field effect transistors. In this project, by using semiconducting ferroelectric materials of selected symmetry with strong spin-orbit coupling, the PI expects to achieve symmetry-protected long-range coherent spin transport via persistent spin helix and switchable spin texture upon changing the ferroelectric polarization. To pursue these goals, the PI will grow high-quality single crystalline ferroelectric semiconductors carrying strong spin-orbit coupling, and fabricate ferroelectric spin valves and field effect transistors. The PI will investigate the spin-polarized band structure and persistent spin helix in the model materials. The PI will reveal the spin lifetime and spin diffusion length in ferroelectric spin valves and field effect transistors. The PI will also study the dynamics of ferroelectric domain structure and effect of ferroelectric domain orientation on persistent spin helix, spin dynamics, spin operation and diffusion. This proposed work will advance the fundamental knowledge needed in resolving the intrinsic dilemma issue between the precise manipulation and effective preservation of spin in spintronic systems with strong spin-orbit interaction.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.