Chirality-induced Spin Generation and Dynamic Nuclear Polarization in n-GaAs

The generation and control of spin-polarized electrons in semiconductors through non-magnetic methods present exciting opportunities for the advancement of spintronics and quantum information science. One approach exploits chiral/helical spin textures in electronic structures, while another leverages the interaction between electron spin and chirality in real space. A key manifestation of such effects of is chirality-induced spin selectivity (CISS), where real-space structural chirality induces spin polarization of electrons from a nonmagnetic (NM) electrode¹. In this work, we demonstrate the effect of CISS can be utilized to generate spin polarization in a conventional semiconductor in a device structure free of any magnetic material. The devices are chiral molecular junctions comprising a normal metal electrode and a self-assembled monolayer of α-helix L-polyalanine (AHPA-L) on n-type GaAs². The spin accumulation in the n-GaAs was measured via the Hanle effect. Our experiments revealed signatures of dynamic nuclear polarization (DNP), a phenomenon where nuclear spin polarization is induced by electron spin polarization, which in turn causes depolarization of the electron spins. This observation has intriguing potential in quantum information science, as DNP involves long-lived nuclear spins, making it a promising candidate as quantum memory for molecular qubits. Our findings suggest a novel pathway for enhancing spintronic devices and advancing quantum information technologies through the combined effects of CISS and DNP.

¹ B.P. Bloom, et. al., Chem. Rev. 124, 1950 (2024).

² T. Liu, Y. Adhikari, H. Wang, et. al., Adv. Mater. 36, 2406347 (2024).