Spinterface chirality-induced spin selectivity effect in bio-molecules

Abstract

The chirality-induced spin selectivity (CISS) effect, namely the dependence of current through a chiral molecule on spin of the electron, was discovered over two decades ago, and has been suggested for various spin- and chirality-related applications. Yet, quite surprisingly, its physical origin remains elusive, and no theoretical description can quantitatively describe it. Here, we propose a theory for the CISS effect in bio-molecular junctions, based on the interplay between spin-orbit coupling in the electrodes, molecular chirality and spin-transfer torque across the electrode-molecule interface. This theory leads to the first ever quantitative analysis of experimental data, and provides insights into the origin of the CISS effect. The theory presented here can be used to analyze past experiments and to design new experiments, which may lead to deeper understanding of what is considered one of the outstanding problems in molecular electronics and nano-scale transport.

Fig. 1. (a) Polarization as a function of voltage for a 25BP CNA chain for different values of e–ph coupling, γ = 0, 0.1, 0.2, 0.3 eV. (b) Polarization as a function of voltage for different molecular lengths of 15,17,…,25 BPs, at γ = 0. (c) Same as (b), for γ = 0.3 eV. See text for other numerical parameters.

Fig. 2. (a) Current–voltage curves for a chain of 25BPs for different values of γ. (b) Differential conductance, dJ/dV, extracted from the currents in (a). (c) Difference between magnetization-dependent currents, J_↑ − J_↓ as a function of voltage, for different values of γ.

Fig. 3. (a) Difference between magnetization-dependent currents, J_↑ − J_↓ as a function of voltage. Data extracted from ref. . (b) Differential conductance dJ/dV extracted from ref. .

Fig. 4. Currents J_σ(V) as a function of voltage, blue and orange encode the Ni electrode magnetization parallel and anti-parallel to the molecular axis. The open markers are the data of ref. , solid lines are theoretical fits. All three samples share the same CISS parameters, namely α_A and α₁ (see text).