Hanle Effect without a Magnet in Chiral Molecular Junctions

Electrical generation of spin polarization in nonmagnetic materials is of broad interest for the underlying physics and spintronics applications. Chirality-induced spin selectivity (CISS) potentially presents a scheme of spin generation and detection entirely free of any magnetic materials. Here we report creation of spin accumulation in n-GaAs via electrical current injection from a Au electrode through a self-assembled monolayer of chiral molecules of alpha-helix polyalanines (AHPA-L). We had previously demonstrated that the CISS effect can manifest in pronounced spin valve signals in similar devices with (Ga,Mn)As as the spin analyzer; here we show that the CISS spin polarization can be detected as the Hanle effect in n-GaAs without using a ferromagnet. The Hanle signals in the GaAs:Si/AHPA-L/Au junctions were found to exhibit universal temperature and bias current dependences with high degrees of consistency. We will present quantitative analysis of the experimental results and discuss their implications on the physical origin of CISS. The work suggests a new scheme of semiconductor spintronics free of any magnetic materials based on the CISS effect.