NSF-BSF: Understanding the Emergence of Spin Polarization at Chiral Interfaces

With support from the Chemical Structure and Dynamics (CSD) program in the Division of Chemistry, Professors Oliver Monti of the University of Arizona and Yonatan Dubi of Ben Gurion University are studying the transmission of electrons through layers of non-magnetic chiral molecules. Electrons can exist in two spin states: spin up or spin down. To separate electrons with different spins, magnetic fields are normally necessary.

However, when electrons pass through layers of chiral molecules, one spin or the other can be preferentially transmitted, thus accomplishing this separation without magnetic fields. The origin of this chirality induced spin selectivity (CISS) effect is extensively debated and remains unclear. Professors Monti, Dubi and their students will combine sophisticated electron spectroscopies with detailed scattering theory to characterize the transmission of electrons passing through chiral molecules.

Their discoveries could provide an experimentally tested and quantitative understanding of CISS, as well as new ways of harnessing spin-dependent effects in quantum-based technologies without the need for magnetic fields or complex device designs. The project will also provide research opportunities for graduate and undergraduate students, as well as contribute to the development of a quantum-enabled STEM workforce.

The overarching goal of the project is to develop, test and implement a quantitative microscopic understanding of CISS. Professors Monti and Dubi will investigate CISS using cutting-edge spin- and angle-resolved photoemission methods from well-characterized and ordered films of near-identical chiral or achiral molecules on highly controlled metal substrates.

Systematic and quantitative experimental observations of energy-, momentum-, and direction-dependence of excess spin, the critical fingerprint of CISS, will be compared with results from quantitatively correct scattering theories that range from mean-field to full microscopic descriptions. Both molecular and substrate parameters that could be responsible for CISS will be isolated and quantified, and their impact tested.

Undergraduate and graduate students will be trained in carrying out highly controlled and sophisticated surface science experiments and computations to shed light on the mechanism of CISS, and to advance novel approaches in quantum information sciences.

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.