Bacteriorhodopsin based non-magnetic spin filters for biomolecular spintronics

Abstract

We discuss spin injection and spin valves, which are based on organic and biomolecules, that offer the possibility to overcome some of the limitations of solid-state devices, which are based on ferromagnetic metal electrodes. In particular, we discuss spin filtering through bacteriorhodopsin in a solid state biomolecular spin valve that is based on the chirality induced spin selectivity (CISS) effect and shows a magnetoresistance of ∼2% at room temperature. The device is fabricated using a layer of bacteriorhodopsin (treated with n-octyl-thioglucoside detergent: OTG-bR) that is adsorbed on a cysteamine functionalized gold electrode and capped with a magnesium oxide layer as a tunneling barrier, upon which a Ni top electrode film is placed and used as a spin analyzer. The bR based spin valves show an antisymmetric magnetoresistance response when a magnetic field is applied along the direction of the current flow, whereas they display a positive symmetric magnetoresistance curve when a magnetic field is applied perpendicular to the current direction.

Light-driven molecular switch for reconfigurable spin filters

“…The results of spin-valve-like measurements displayed in Fig. 2b show a clear up-spin selectivity (the spin angular momentum is oriented parallel to the direction of electron propagation) for the M-trans device and down-spin selectivity (the spin angular momentum is oriented antiparallel to the direction of electron propagation) for the P-cis device, whose directions are consistent with those reported in previous CISS experiments 14,23,27,38 . Meanwhile, in the racemic compound, no MR signal was found (Fig.…”

“…The absolute MR value of ~2% observed at each state is insignificant compared with other CISS experiments 23,35,37,38 . This is likely owing to the unpolarized leakage currents through the pinholes in the OCA films because the OCAs are not perfectly packed in the films.…”

“…Moreover, the CISS effect was already demonstrated in several applications such as magnetic memory devices 27–29 , spin-injection devices 30 , water splitting 31,32 , and enantiomer separation 33,34 . However, in all of the cases above, chiral molecules used in the experiments are static molecules such as DNAs 14,19,22,33 , helicenes 18,23 , amino acids 35,36 , and peptides 20,21,25,26,28,29,37,38 . Hence, the manipulation of spin-polarization (SP) direction by external stimuli has not been realized yet.…”

Spin‐selective electron transmission through self‐assembled monolayers of double‐stranded peptide nucleic acid

“…3 Since its discovery, CISS has been evidenced by different methods, including cyclic voltammetry, 11 magnetic AFM, [12][13][14] magnetoresistance, 15,16 spin-resolved photoemission, 1 and Hall measurements. 11,17 Besides in dsDNA, CISS was found in oligopeptides, 13,[18][19][20] bacteriorhodopsin, [21][22][23] alkene-based artificial molecular motors, 16 and further molecular systems.…”

Spin Injection and Transport in Organic Materials

“…Chiral molecules can self-assemble into nanostructures, superstructures and even macrostructures, and their unique structural spin-orbit coupling can produce many novel spin-charge correlation phenomena. “Chiral Electronics” or “Chiral Spintronics” has quietly appeared [98,99,100,101,102,103,104]. Researches on organic chiral spin-related phenomena not only promote the development of organic spintronics, promote the intersection of physics and chemistry and micro-nano electronics and develop the application of organic chiral molecules and fibers in functions such as electromagnetism optics and others; but also contribute to understand the information storage and transmission of biological macromolecules, provide a physical perspective of the complex life and design more organic (spin) electronics that are stretchable, wearable or implantable.…”