Mechanism for Electrostatically Generated Magnetoresistance in Chiral Systems without Spin-Dependent Transport

Abstract

Significant attention has been drawn to electronic transport in chiral materials coupled to ferromagnets in the chirality-induced spin selectivity (CISS) effect. A large magnetoresistance (MR) is usually observed, which is widely interpreted to originate from spin (dependent) transport. However, there are severe discrepancies between the experimental results and the theoretical interpretations, most notably the apparent failure of the Onsager reciprocity relations in the linear response regime. We provide an alternative mechanism for the two terminal MR in chiral systems coupled to a ferromagnet. For this, we point out that it was observed experimentally that the electrostatic contact potential of chiral materials on a ferromagnet depends on the magnetization direction and chirality. The mechanism that we provide causes the transport barrier to be modified by the magnetization direction, already in equilibrium, in the absence of a bias current. This strongly alters the charge transport through and over the barrier, not requiring spin transport. This provides a mechanism that allows the linear response resistance to be sensitive to the magnetization direction and also explains the failure of the Onsager reciprocity relations. We propose experimental configurations to confirm our alternative mechanism for MR.

Chirality-Induced Spin Selectivity: Analysis of Density Functional Theory Calculations

“…Interestingly, recent low-temperature spin-polarized scanning tunneling microscopy and spectroscopy measurements on single chiral heptahelicene molecules sublimed in vacuo from a racemic mixture onto the single-crystalline cobalt bilayer of nano-islands on a Cu(111) surface found that thermal enhancement mechanisms are not the essential ingredients for CISS . Moreover, an alternative mechanism was suggested for the origin of the two-terminal magnetoresistance linear response in chiral systems coupled to a ferromagnet …”