Spin sensitive electron transmission through helical potentials

Abstract

We calculate the transmission coefficient for electrons passing through the helically shaped potential barrier which can be, for example, produced by DNA molecules. Introduction. In recent years, it was discovered that electron transmission through ordered thin films of chiral molecules is highly spin selective 1-5 . This effect was termed as chiral-induced spin selectivity (CISS) effect 4 (for details see review 6 and Refs. therein). In experiments 2,4 , the transmission of photoelectrons through self-assembled monolayers (SAMs) of doublestranded DNA (dsDNA) on gold has been studied. The spin polarization (SP) of electrons ejected from Au substrate and transmitted through SAM of dsDNA was measured and the strong SP, which is defined as 4 P = (I ↑ − I ↓ )/(I ↑ + I ↓ ) was observed. Here I ↑ and I ↓ are the intensities of the signals corresponding to the SP oriented parallel and antiparallel to the electrons' velocity, respectively.Recently, different models have been proposed 7-10 to explain experimental results. A scattering theory in the first Born approximation has been applied to obtain the SP in the differential cross section of electrons moving through chiral molecules with energies above the vacuum level 8 . The model of point charges placed along a helical line is considered in a tight binding approximation for electronic structure of the helix and the transmission of distinct electron spin state is computed by the Landauer formulation 9 . The SP conductance through a metal-DNA-metal structure is calculated in a tight binding picture 10 . Although all these studies differ in details, they possess similar physical basis. Each of them is based on accounting of the spin-orbit interaction (SOI) of an electron that is moving through a helical potential. In other words, describing different aspects of the problem, approaches are based on the Schrödinger equation 11

Spin Filtering through Single‐Wall Carbon Nanotubes Functionalized with Single‐Stranded DNA

“…Thus these mechanisms alone cannot explain the large spin dependent barrier height discussed above. Therefore this work should be viewed within the framework of the Rashba spin-orbit interaction induced by the inversion asymmetric helicoidal electric field of the ssDNA [16,17] . It is to be noted that similar unusual large splitting between the two spin states has been observed in spin selective conduction through double stranded DNA [9] .…”

“…Another candidate that has been proposed theoretically as a spin filter is single wall carbon nanotube (SWCNT), wrapped by a chiral molecule (such as single-stranded (ss)-DNA), which creates a helical potential in the tube [16,17] . Carbon nanotubes (CNTs), which can be loosely described as single graphitic sheet rolled into a cylinder, have been explored extensively in the area of spintronics [18] .…”

Spin-dependent electron transport in protein-like single-helical molecules

“…Additionally, the CISS effect opens new opportunities for using chiral molecules in spintronic applications and could provide a deeper understanding of the spin effects in biological processes. For the above reasons, there has been considerable interest in the spin transport along various chiral systems including dsDNA (8)(9)(10)(11), single-stranded DNA (ssDNA) (12)(13)(14)(15), and carbon nanotubes (16). However, no spin selectivity was measured in the ssDNA above the experimental noise (5).…”

Spin filtering in all-electrical three-terminal interferometers

“…[36][37][38][39][40][41][42][43][44][45] However, there is still no consensus on the appropriate theory. To explain the CISS effect without invoking a magnetic field, several earlier theories calculated the current between a single source and a single drain, but effectively added coupling of the system to additional reservoirs.…”