  Central to spintronics is the interconversion between electronic charge and
spin currents, and this can arise from the chirality-induced spin selectivity
(CISS) effect. CISS is often studied as magnetoresistance (MR) in two-terminal
(2T) electronic devices containing a chiral (molecular) component and a
ferromagnet. However, fundamental understanding of when and how this MR can
occur is lacking. Here, we uncover an elementary mechanism that generates such
a MR for nonlinear response. It requires energy-dependent transport and energy
relaxation within the device. The sign of the MR depends on chirality, charge
carrier type, and bias direction. Additionally, we reveal how CISS can be
detected in the linear response regime in magnet-free 2T devices, either by
forming a chirality-based spin-valve using two or more chiral components, or by
Hanle spin precession in devices with a single chiral component. Our results
provide operation principles and design guidelines for chirality-based
spintronic devices and technologies.
