scholarly journals Quantum Interference and Spin Filtering Effects in Photo-responsive Endoperoxide Based Single Molecular Device

2021 ◽  
Author(s):  
Ashima Bajaj ◽  
Rishu Khurana ◽  
Md. Ehesan Ali
Keyword(s):  
Single Molecule ◽  
Quantum Interference ◽  
Density Functional ◽  
Reaction Pathway ◽  
Stimuli Responsive ◽  
Spin Configuration ◽  
De Broglie Waves ◽  
Filtering Efficiency ◽  
External Stimuli ◽  
Spin Filtering

<div>The development of stimuli responsive systems that can switch between two distinct spin states under the application of an external stimuli has always remained an illusory challenge. Here, we report a stimuli-based spin filter by utilizing photo-responsive endoperoxide (EPO) based single molecule device. The photo-irradiation on EPO triggers the homolytic cleavage of the peroxide O-O bond generating diradical intermediate centered on two O-atoms which facilitates high spin filtering efficiency when placed between gold electrodes. The broken conjugated scenario due to peroxide bridge of EPO hinders the propagation of de-Broglie waves across the molecular skeleton. While the diradical intermediate of EPO yields high conductance for one of the spin configuration. The transmission characteristics of various photoproducts along the photochemical reaction pathway of EPO are also investigated using density functional theory in combination with non-equilibrium Green’s function (NEGF-DFT) technique. We demonstrate the key role played by Quantum Interference (QI) effects in dramatic modulation of conductance arising due to different degree of conjugation along the reaction pathway of EPO.</div><div><br></div>

scholarly journals Quantum Interference and Spin Filtering Effects in Photo-responsive Endoperoxide Based Single Molecular Device

2021 ◽  
Author(s):  
Ashima Bajaj ◽  
Rishu Khurana ◽  
Md. Ehesan Ali
Keyword(s):  
Single Molecule ◽  
Quantum Interference ◽  
Density Functional ◽  
Reaction Pathway ◽  
Stimuli Responsive ◽  
Spin Configuration ◽  
De Broglie Waves ◽  
Filtering Efficiency ◽  
External Stimuli ◽  
Spin Filtering

<div>The development of stimuli responsive systems that can switch between two distinct spin states under the application of an external stimuli has always remained an illusory challenge. Here, we report a stimuli-based spin filter by utilizing photo-responsive endoperoxide (EPO) based single molecule device. The photo-irradiation on EPO triggers the homolytic cleavage of the peroxide O-O bond generating diradical intermediate centered on two O-atoms which facilitates high spin filtering efficiency when placed between gold electrodes. The broken conjugated scenario due to peroxide bridge of EPO hinders the propagation of de-Broglie waves across the molecular skeleton. While the diradical intermediate of EPO yields high conductance for one of the spin configuration. The transmission characteristics of various photoproducts along the photochemical reaction pathway of EPO are also investigated using density functional theory in combination with non-equilibrium Green’s function (NEGF-DFT) technique. We demonstrate the key role played by Quantum Interference (QI) effects in dramatic modulation of conductance arising due to different degree of conjugation along the reaction pathway of EPO.</div><div><br></div>

Quantum Interference and Spin Filtering Effects in Photo-responsive Single Molecular Device

2021 ◽  
Author(s):  
Ashima Bajaj ◽  
Rishu Khurana ◽  
Md. Ehesan Ali
Keyword(s):  
Quantum Interference ◽  
Spin States ◽  
Molecular Device ◽  
Stimuli Responsive ◽  
Responsive Systems ◽  
External Stimuli ◽  
Spin Filtering

The development of stimuli responsive systems that can switch between two distinct spin states under the application of an external stimuli has always remained an illusory challenge. Here, we report...

A density functional theory approach to the magnetic properties of a coupled single-molecule magnet (Mn7)2 complex — An entangled qubit pair candidate

2013 ◽  
Vol 91 (9) ◽  
pp. 866-871 ◽  
Author(s):  
Silvia Gómez-Coca ◽  
Eliseo Ruiz
Keyword(s):  
Density Functional Theory ◽  
Single Molecule ◽  
Exchange Coupling ◽  
Density Functional ◽  
Relative Strength ◽  
Coupling Constants ◽  
Basis Set ◽  
Theory Approach ◽  
Functional Theory ◽  
Spin Configuration

The exchange coupling constants of a Mn14 complex constituted by two weakly coupled Mn7 moieties were calculated using two different density functional theory (DFT) approaches: the Perdew–Burke–Ernzerhof (PBE) functional with a numerical basis set and the hybrid Becke, three-parameter Lee–Yang–Parr (B3LYP) functional employed with a Gaussian basis set. The sign and relative strength of the exchange coupling constants calculated with both methods were consistent; as expected, the values calculated with the PBE functional were slightly overestimated, as corroborated by comparison with the experimental magnetic susceptibility curve. Both methods gave a ground spin configuration of S = 3/2 for the Mn7 moiety, which was weakly antiferromagnetically coupled with the other Mn7 fragment, leading to an S = 0 ground spin configuration for the entire Mn14 complex.

scholarly journals The Anomalous Effect of Quantum Interference in Organic Spin Filters

2020 ◽  
Author(s):  
Ashima Bajaj ◽  
Prabhleen Kaur ◽  
Aakanksha Sud ◽  
Marco Berritta ◽  
Md. Ehesan Ali
Keyword(s):  
Quantum Interference ◽  
Density Functional ◽  
Organic Radicals ◽  
Spin Coupling ◽  
Anomalous Effect ◽  
Spin Filters ◽  
Molecular Conductance ◽  
Spin Spin Coupling ◽  
Spin Filtering

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>

scholarly journals The Anomalous Effect of Quantum Interference in Organic Spin Filters

2020 ◽  
Author(s):  
Ashima Bajaj ◽  
Prabhleen Kaur ◽  
Aakanksha Sud ◽  
Marco Berritta ◽  
Md. Ehesan Ali
Keyword(s):  
Quantum Interference ◽  
Density Functional ◽  
Organic Radicals ◽  
Spin Coupling ◽  
Anomalous Effect ◽  
Spin Filters ◽  
Molecular Conductance ◽  
Spin Spin Coupling ◽  
Spin Filtering

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>

scholarly journals Switching Quantum Interference in Phenoxyquinone Single Molecule Junction with Light

Nanomaterials ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1544
Author(s):  
Abdalghani Daaoub ◽  
Sara Sangtarash ◽  
Hatef Sadeghi
Keyword(s):  
Molecular Structure ◽  
Single Molecule ◽  
Quantum Interference ◽  
Significant Variation ◽  
Light Stimulus ◽  
New Paradigm ◽  
Molecule Junction ◽  
Single Molecule Junction ◽  
External Stimuli

Quantum interference (QI) can lead to large variations in single molecule conductance. However, controlling QI using external stimuli is challenging. The molecular structure of phenoxyquinone can be tuned reversibly using light stimulus. In this paper, we show that this can be utilized to control QI in phenoxyquinone derivatives. Our calculations indicate that, as a result of such variation in molecular structure of phenoxyquinone, a crossover from destructive to constructive QI is induced. This leads to a significant variation in the single molecule conductance by a couple of orders of magnitude. This control of QI using light is a new paradigm in photosensitive single molecule switches and opens new avenues for future QI-based photoswitches.

scholarly journals Spin-Transport Tuning of Individual Magnetic Mn-Salophen Molecule via Chemical Adsorption

Molecules ◽  
2019 ◽  
Vol 24 (9) ◽  
pp. 1747 ◽  
Author(s):  
Feifei Li ◽  
Jing Huang ◽  
Jianing Wang ◽  
Qunxiang Li
Keyword(s):  
Single Molecule ◽  
Magnetic Moment ◽  
Density Functional ◽  
Spin Transport ◽  
Density Functional Theory Calculations ◽  
Chemical Adsorption ◽  
Adsorption Effect ◽  
Single Molecule Level ◽  
Filtering Effect ◽  
Spin Filtering

Control over spin states at the single molecule level is a key issue in the emerging field of molecular spintronics. Here, we explore the chemical adsorption effect on the magnetic and spin-transport properties of individual magnetic molecule by performing extensive density functional theory calculations in combining with non-equilibrium Green’s function method. Theoretical results clearly reveal that the molecular magnetic moment of Mn-salophen can be effectively tuned by adsorbing F and CO on the central Mn cation, while the adsorbed NO molecule quenches the molecular magnetic moment. Without chemical adsorption, the currents through Mn-salophen molecular junction just show a little distinction for two spin channels, which agrees well with previous investigation. Remarkably, the conductive channel can be switched from the spin-up electrons to the spin-down electrons via adsorbing F and CO, respectively, and the corresponding two Mn-salophen molecular junctions with chemical modifications display nearly perfect spin-filtering effect. The observed spin switch and the predicted spin-filtering effect via chemical adsorption indicates that Mn-salophen holds potential applications in molecular spintronic devices.

Fine Spin Filtering Effect in Co-Phthalocyanine Molecule Induced by the Spin Polarization of Co Atom

2014 ◽  
Vol 597 ◽  
pp. 127-130
Author(s):  
Yan Hong Zhou ◽  
X.H. Qiu ◽  
L.L. Zhou ◽  
Y.L. Peng
Keyword(s):  
Single Molecule ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Underlying Mechanism ◽  
Spintronic Devices ◽  
Spin Direction ◽  
Spin Polarized ◽  
Phthalocyanine Molecule ◽  
Filtering Effect ◽  
Spin Filtering

Spintronic devices will play a very important role in future information technology. In this study, By spin-polarized density-functional theory calculations combined with the Keldysh nonequilibrium Green’s method, the effect of the spin direction of Co atom in Co- phthalocyanine molecule in modulating spin filtering effects under external biases are investigated. Here, an individual single molecule Co-phthalocyanine is sandwiched between two infinite 8-zigzag-graphene nanoribbon electrodes. we find that the spin direction of the Co atom relative to the magnetic polarization of the left and right electrodes can improve the spin filtering effect greatly. when the polarization direction of the two electrodes is antiparallel and the polarization of Co atom in the Co-phthalocyanine molecule upward, the configuration posesses almost perfectly spin-filter effect. The underlying mechanism of the perfect spin filtering action is applied.

SPIN-FILTERING, RECTIFYING AND NEGATIVE DIFFERENTIAL RESISTANCE BEHAVIORS IN Co(dmit)2 MOLECULAR DEVICES WITH MONATOMIC (C, Fe, Au) ELECTRODES

SPIN ◽  
2014 ◽  
Vol 04 (02) ◽  
pp. 1440016
Author(s):  
SHENLANG YAN ◽  
MENGQIU LONG ◽  
XIAOJIAO ZHANG ◽  
JUN HE ◽  
HUI XU ◽  
...  
Keyword(s):  
Single Molecule ◽  
Negative Differential Resistance ◽  
Density Functional ◽  
Electrode Materials ◽  
Energy Levels ◽  
Differential Resistance ◽  
Interesting Phenomenon ◽  
Filtering Effect ◽  
Dependent Transport ◽  
Spin Filtering

Using nonequilibrium Green's functions (NEGFs) combined with the density functional theory (DFT), we study the electronic transport properties of a single molecule magnet Co ( dmit )2, which is sandwiched between two monatomic chain electrodes, and the different electrode materials carbon, iron and gold, have been considered. The results show that the electrodes play a crucial role in the spin-dependent transport of the Co ( dmit )2 molecular device, and some interesting phenomenon, such as perfect spin-filtering effect, rectifying and negative differential resistance (NDR) can be observed. We demonstrated that the magnetic Fe electrode can lead to high spin-flittering effect, and the different hybridization and alignment of energy levels between the molecule and the electrodes may be responsible for the rectification performance, and the distributions (delocalization or localization) of the frontier molecular orbitals under different bias result in the NDR behaviors. These characteristics could be used in the study of spin physics and the realization of nanospintronic devices.

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