Nonmagnetic single-molecule spin-filter based on quantum interference

Pal, Atindra Nath; Li, Dongzhe; Sarkar, Soumyajit; Chakrabarti, Sudipto; Vilan, Ayelet; Kronik, Leeor; Smogunov, Alexander; Tal, Oren

doi:10.1038/s41467-019-13537-z

“…Therefore, molecular orbitals are expected to preserve their symmetry and localized nature. In the collinear magnetic case without SOC, it has been shown that a nonmagnetic organic molecule can act as a "halfmetallic" conductor due to either orbital symmetry arguments [27,28] or quantum interference effects [29,30], leading to nearly fully spin-polarized conduction. In addition, a nearly perfect spin filtering was reported when a vanadium-benzene wire is placed between two magnetic electrodes [31].…”

Section: Introductionmentioning

confidence: 99%

Giant anisotropic magnetoresistance through a tilted molecular π -orbital

Li

¹

,

Pauly

²

2020

Phys. Rev. Research

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Anisotropic magnetoresistance (AMR), originating from spin-orbit coupling (SOC), is the sensitivity of the electrical resistance in magnetic systems to the direction of spin magnetization. Although this phenomenon has been experimentally reported for several nanoscale junctions, a clear understanding of the physical mechanism behind it is still elusive. Here we discuss a concept based on orbital symmetry considerations to attain a significant AMR of up to 95% for a broad class of π-type molecular spin valves. It is illustrated at the benzene-dithiolate molecule connecting two monoatomic nickel electrodes. We find that SOC opens, via spin-flip events at the ferromagnet-molecule interface, a conduction channel, which is fully blocked by symmetry without SOC. Importantly, the interplay between two transport channels turns out to depend strongly on the magnetization direction in the nickel electrodes due to the tilting of molecular orbitals. Moreover, due to multiband quantum interference, appearing at the band edge of nickel electrodes, a transmission drop is observed just above the Fermi energy. Altogether, these effects lead to a significant AMR around the Fermi level, which even changes sign. Our theoretical understanding, corroborated in terms of ab initio calculations and simplified analytical models, reveals the general principles for an efficient realization of AMR in molecule-based spintronic devices.

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“…23,24 But only few reports have described QI effects in systems exhibiting spin polarization. [25][26][27] Recently, Li et al proposed a mechanism for tuning the spin filtering ratio based on QI effects in a nickel based junction. 28 Ratner and coworkers have demonstrated that how DQI features can be controlled by addition of a donor or acceptor group to the polyacetylene chain bridging graphene nanoribbons (ZGNR).…”

Section: Graphical Toc Entrymentioning

confidence: 99%

The Anomalous Effect of Quantum Interference in Organic Spin Filters

Bajaj

¹

,

Kaur²,

Sud³

et al. 2020

Preprint

0

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The molecular topology in the single-molecular nano-junctions through which the de Broglie wave propagates plays a crucial role in controlling the molecular conductance. The enhancement and reduction of the conductance due to constructive and destructive Quantum Interference (QI) in para and meta connected molecules respectively has already been well established. Herein, we investigated the influence of QI on spin transport in the molecular junctions containing organic radicals as magnetic centres. The role of the localized spins on the QI as well as on spin filtering capability is investigated employing density functional theory in combination with non-equilibrium Green's function (NEGF-DFT) techniques. Various organic radicals including nitroxide (NO), phenoxy (PO) and methyl (CH2) radicals attached to the central benzene ring of pentacene with different terminal connections (para and meta) to gold electrodes are examined. Due to more obvious QI effects, para connected pentacene is found to be more conductive than meta one. Surprisingly, on incorporating a radical centre, along with spin filtering, a significant quenching of QI effects is observed which manifests itself in such a way that the conductance of meta coupled radicals is found to be more than para by two orders of magnitude. The decoherence induced by radical centre is analysed and discussed in terms of spin-spin coupling of radical's unpaired electron with the tunneling electrons.<br>

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“…24,25 But only few reports have described QI effects in systems exhibiting spin polarization. [26][27][28][29] Recently, Li et al proposed a mechanism for tuning the spin filtering ratio based on QI effects in a nickel based junction. 30 Ratner and coworkers have demonstrated that how DQI features can be controlled by addition of a donor or acceptor group to the polyacetylene chain bridging graphene nanoribbons (ZGNR).…”

Section: Introductionmentioning

confidence: 99%

The Anomalous Effect of Quantum Interference in Organic Spin Filters

Bajaj

¹

,

Kaur²,

Sud³

et al. 2020

Preprint

0

View full text Add to dashboard Cite

The molecular topology in the single-molecular nano-junctions through which the de Broglie wave propagates plays a crucial role in controlling the molecular conductance. The enhancement and reduction of the conductance due to constructive and destructive Quantum Interference (QI) in para and meta connected molecules respectively has already been well established. Herein, we investigated the influence of QI on spin transport in the molecular junctions containing organic radicals as magnetic centres. The role of the localized spins on the QI as well as on spin filtering capability is investigated employing density functional theory in combination with non-equilibrium Green's function (NEGF-DFT) techniques. Various organic radicals including nitroxide (NO), phenoxy (PO) and methyl (CH2) radicals attached to the central benzene ring of pentacene with different terminal connections (para and meta) to gold electrodes are examined. Due to more obvious QI effects, para connected pentacene is found to be more conductive than meta one. Surprisingly, on incorporating a radical centre, along with spin filtering, a significant quenching of QI effects is observed which manifests itself in such a way that the conductance of meta coupled radicals is found to be more than para by two orders of magnitude. The decoherence induced by radical centre is analysed and discussed in terms of spin-spin coupling of radical's unpaired electron with the tunneling electrons.<br>

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Nonmagnetic single-molecule spin-filter based on quantum interference

Cited by 70 publications

References 41 publications

Giant anisotropic magnetoresistance through a tilted molecular π -orbital

Giant anisotropic magnetoresistance through a tilted molecular π -orbital

The Anomalous Effect of Quantum Interference in Organic Spin Filters

The Anomalous Effect of Quantum Interference in Organic Spin Filters

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