Abstract
The chiral-induced spin selectivity (CISS) effect entails spin-selective electron transmission through chiral molecules. In the present study, the spin filtering ability of chiral, helical oligopeptide monolayers of two different lengths is demonstrated using magnetic conductive probe atomic force microscopy. Spin-specific nanoscale electron transport studies elucidate that the spin polarization is higher for 14-mer oligopeptides than that of the 10-mer. We also show that the spin filtering ability can be tuned by changing the tip-loading force applied on the molecules. The spin selectivity decreases with increasing applied force, an effect attributed to the increased ratio of radius to pitch of the helix upon compression and increased tilt angles between the molecular axis and the surface normal. The method applied here provides new insights into the parameters controlling the CISS effect.
Highlights
The concept of molecular electronics, in which a molecular junction is formed by attaching a molecule between two electrodes, was born with the proposition that molecules may act as a rectifying device.1 Subsequently, this research has evolved in various directions, for instance, design of molecular transistors, switches, optoelectronics, and spintronics to name a few.2–4 Molecular spintronics, in which the electron spin is exploited to store and transport information, has attracted much attention due to the ability to manipulate spin of the electron, rather than charge, in an energetically efficient way.5 Organic molecules are attractive for this application since they have relatively long spin coherence times, due to the weak spin-orbit and hyperfine interactions
The chiral-induced spin selectivity (CISS) effect relates to the ability of chiral molecules to transmit electrons in a spin-selective manner, the molecules act as spin filters
The present study demonstrates the use of Conductive probe atomic force microscopy (CP-atomic force microscopy (AFM)) to study the spin dependent electron transfer through oligopeptide monolayers
Summary
The concept of molecular electronics, in which a molecular junction is formed by attaching a molecule between two electrodes, was born with the proposition that molecules may act as a rectifying device. Subsequently, this research has evolved in various directions, for instance, design of molecular transistors, switches, optoelectronics, and spintronics to name a few. Molecular spintronics, in which the electron spin is exploited to store and transport information, has attracted much attention due to the ability to manipulate spin of the electron, rather than charge, in an energetically efficient way. Organic molecules are attractive for this application since they have relatively long spin coherence times, due to the weak spin-orbit and hyperfine interactions. In which the electron spin is exploited to store and transport information, has attracted much attention due to the ability to manipulate spin of the electron, rather than charge, in an energetically efficient way.. The chiral-induced spin selectivity (CISS) effect is a recent addition to the arsenal of spintronics. The CISS effect relates to the ability of chiral molecules to transmit electrons in a spin-selective manner, the molecules act as spin filters.. Several chiral molecular species including DNA, oligopeptides, bacteriorhodopsin (bR), a chiral conductive polymer,18 1, 2-diphenyl-1,2-ethanediol (DPED), helicenes, and recently chiral CdSe quantum dots 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, by exposure to light, or by varying the temperature.. The spin filtering ability can be tuned by various means, for example, by varying the length of the chiral molecule, by exposure to light, or by varying the temperature. The sign of the favored spin can be reversed by light, as was shown for an oligopeptide-CdSe hybrid and 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. It was found that for given oligomers (DNA or peptides) longer molecules lead to better spin filtering. there is abundant experimental evidence that the CISS effect depends on the structural parameters of the chiral molecules
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