Spin-Dependent Ionization of Chiral Molecular Films

Abstract

Spin selectivity in photoemission from ferromagnetic substrates functionalized with chiral organic films was analyzed by ultraviolet photoelectron spectroscopy at room temperature. Using radiation with photon energy greater than the ionization potential of the adsorbed molecules, photoelectrons were collected that originated from both underlying ferromagnetic substrates and the organic films, with kinetic energies in the range of ca. 0-18 eV. We investigated chiral organic films composed of self-assembled monolayers of α-helical peptides and electrostatically adsorbed films of the protein, bovine serum albumin, with different α-helix and β-sheet content. Ultraviolet photoelectron spectral widths were found to depend on substrate magnetization orientation and polarization, which we attribute to helicity-dependent molecular ionization cross sections by photoelectron impact, possibly resulting in spin-polarized holes. These interactions between spinpolarized photoelectrons and chiral molecules are physically manifested as differences in the measured photoionization energies of the chiral molecular films. Substrate magnetizationdependent ionization energies and work function values were deconvoluted using surface charge neutralization techniques, permitting the measurement of relative spin-dependent energy barriers to transmission through chiral organic films.

Organic-to-inorganic structural chirality transfer in a 2D hybrid perovskite and impact on Rashba-Dresselhaus spin-orbit coupling

“…These structural insights, coupled with theoretical findings in our work, enable the discovery and design of an emerging class of multifunctional hybrid systems with an amalgam of semiconducting, chiroptical, and spin-dependent properties. Indeed, the combination of chiral induced spin selectivity of chiral organic molecules [56][57][58][59][60][61][62] and an intrinsic RD spin-splitting in the inorganic framework is a hitherto unexplored aspect unique to 2D chiral HOIPs and might have practical implications in future HOIP-based spintronics. Further, the structural chirality transfer and ensuing lowering of symmetry within the inorganic sublattice opens up a gateway to other emergent properties such as nonlinear light-matter interactions and piezo-/ferroelectricity, not just in 2D HOIPs but also in related diverse low-dimensional metal halide hybrids.…”

Toward a First-Principles Evaluation of Transport Mechanisms in Molecular Wires

“…[2][3][4] Moreover, approaches for exploiting the spin-polarization properties of diamagnetic helical molecules, such as proteins or DNA, have been suggested in the past, where chiral-induced spin selectivity can be used to design more efficient water-splitting or memory devices. [5][6][7][8][9][10][11] Besides potential technological applications, the field of molecular electronics is appealing due to its significance for fundamental science, offering insights into molecules under unusual circumstances. There are continuing efforts to study charge transport processes in biomolecules like peptides, enzymes and DNA, as they are of vital importance to every living organism, for example in the context of oxidative DNA damage.…”

Highly Efficient and Tunable Filtering of Electrons' Spin by Supramolecular Chirality of Nanofiber‐Based Materials

“…The spintronic devices based on CISS effect are expected to be more compact and amenable to miniaturization. The spin‐polarization properties of various chiral molecules have been studied and typically the upper limit of spin selectivity was about 60% at room temperature, which corresponds to a ratio of about four to one between the two spin states . To realize spintronic devices based on the CISS effect, a much higher level of spin selectivity at room temperature and a way to easily switch the spin state is desired.…”