title: Continuum model for chiral induced spin selectivity in helical molecules.
abstract: A minimal model is exactly solved for electron spin transport on a helix. Electron transport is assumed to be supported by well oriented p(z) type orbitals on base molecules forming a staircase of definite chirality. In a tight binding interpretation, the spin-orbit coupling (SOC) opens up an effective π(z) - π(z) coupling via interbase p(x,y) - p(z) hopping, introducing spin coupled transport. The resulting continuum model spectrum shows two Kramers doublet transport channels with a gap proportional to the SOC. Each doubly degenerate channel satisfies time reversal symmetry; nevertheless, a bias chooses a transport direction and thus selects for spin orientation. The model predicts (i) which spin orientation is selected depending on chirality and bias, (ii) changes in spin preference as a function of input Fermi level and (iii) back-scattering suppression protected by the SO gap. We compute the spin current with a definite helicity and find it to be proportional to the torsion of the chiral structure and the non-adiabatic Aharonov-Anandan phase. To describe room temperature transport, we assume that the total transmission is the result of a product of coherent steps.
authors.affiliation: Centro de Física, Instituto Venezolano de Investigaciones Científicas, 21827, Caracas 1020 A, Venezuela.
authors.forename: Ernesto
authors.initials: E
authors.lastname: Medina
authors.affiliation: IMDEA Nanoscience, Cantoblanco, 28049 Madrid, Spain.
authors.forename: Luis A
authors.initials: LA
authors.lastname: González-Arraga
authors.affiliation: Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Finkelstein-Shapiro
authors.affiliation: Centro de Física, Instituto Venezolano de Investigaciones Científicas, 21827, Caracas 1020 A, Venezuela.
authors.forename: Bertrand
authors.initials: B
authors.lastname: Berche
authors.affiliation: Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287, USA.
authors.forename: Vladimiro
authors.initials: V
authors.lastname: Mujica