Spin Filtering in Electron Transport Through Chiral Oligopeptides

Abstract

We report on the observation of chirality induced spin selectivity for electrons transmitted through monolayers of oligopeptides, both for energies above the vacuum level as well as for bound electrons and for electrons conducted through a single molecule. The dependence of the spin selectivity on the molecular length is measured in an electrochemical cell for bound electrons and in a photoemission spectrometer for photoelectrons. The length dependence and the absolute spin polarization are similar for both energy regimes. Single molecule conductance studies provide an effective charge transport barrier between the two spin channels and it is found to be on the order of 0.5 eV

Structure dependent spin selectivity in electron transport through oligopeptides

“…Similar observations were reported earlier. 13,22 Third, and most importantly, the spin polarization is reduced when the loading force on the tip increases. In addition, the data indicate that a higher spin polarization is obtained with the longer oligopeptide.…”

“…6,7 Several chiral molecular species including DNA, [8][9][10][11][12] oligopeptides, [13][14][15] bacteriorhodopsin (bR), 16,17 a chiral conductive polymer, 18 1, 2-diphenyl-1,2-ethanediol (DPED), 19 helicenes, 20 and recently chiral CdSe quantum dots 21 have demonstrated efficient spin filtering. The spin filtering ability can be tuned by various means, for example, by varying the length of the chiral molecule, 8,9,13 by exposure to light, 22 or by varying the temperature. 23 The sign of the favored spin can be reversed by light, as was shown for an oligopeptide-CdSe hybrid 22 and also by lowering the temperature, which causes cold denaturation of the peptide-made monolayers, as seen in an oligopeptide-CdSe hybrid studied in the Hall configuration.…”

“…23 It was also found that for given oligomers (DNA or peptides) longer molecules lead to better spin filtering. 8,9,13 Thus, there is abundant experimental evidence that the CISS effect depends on the structural parameters of the chiral molecules.…”

Effect of gate voltage on spin transport alongα-helical protein

“…Contrary to the dependence of G ↑ on N , P s increases monotonically with N in the absence of gate voltage, which is consistent with the experiment. 27 While for V g = 0 in the P s -N curve, the value of the same figure peak increases with N at first and then tends to saturation by further increasing N , especially in the case of large V g . The larger V g corresponds to the smaller values of G ↑ and P s , which is independent of N , because of the gating effect.…”

Solitons in a nonlinear model of spin transport in helical molecules

“…In the last decade, a large variety of experiments have shown the existence of chiral spin-selectivity in organic helical molecules [6][7][8][9][10][11][12][13][14]. This effect results from the spinorbit coupling (SOC) between the electronic momentum and the molecular electric field created by the helical arrangement of molecular dipoles.…”