Charge-Spin Conversions and Nonreciprocal Transport in Chiral Materials

Non-technical Abstract: Semiconductor microelectronics is at the heart of today’s information technologies and indispensable for many other utilities. Conventional semiconductor microelectronics utilize only the charge of electrons. It has been demonstrated that harnessing the spin, or the intrinsic magnetic property, of electrons can not only greatly enhance the performance, such as dramatically reduce power consumption, but also produce fundamentally new functionalities such as nonvolatility and reconfigurable logics. An essential ingredient of spin-based semiconductor electronics is the efficient inter-conversions between electronic charge current and spin polarization. This project aims to explore new means of generation, control, and detection of polarized spins in semiconductors by exploiting electron motion in chiral structures, i.e. materials that exhibit distinct handedness. The pure-electronic and magnet-free methods of generating well-aligned electron spins hold the potential of enabling spin-based microelectronics free of any magnetic materials. The project therefore comprises an invaluable combination of basic science research and technology development, providing an effective venue of workforce development for both academia and the semiconductor industry. Technical Abstract: Efficient inter-conversions of charge and spin states are central to fundamental research and device functions of spintronics and quantum computation. Of particular interest are electrical creation of spin polarization and its readout as charge signals without using any ferromagnetic components. This project investigates how structural chirality engenders spin selectivity and, more generally, nonreciprocal transport effects beyond linear response, in three distinct classes of chiral materials: self-assembled monolayers of chiral organic molecules, inorganic chiral crystals, and hybrid organic-inorganic perovskites. An immediate goal of the research is to elucidate the physics underlying the effect of chirality-induced spin selectivity (CISS), where spin polarization emerges from charge motion in materials exhibiting intrinsic structural chirality. More broadly, the research examines the general roles of structural chirality in emergent electronic excitations and novel transport effects from symmetry-breaking, electron correlations, and nontrivial band topology. The research could lead to a conceptually new magnet-free and fully electrical scheme for the generation, control, detection, and utilization of polarized spins in semiconductors. 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.