Effects of dephasing on the spin-dependent currents and noise power in a molecular junction

Fouladi, A. Ahmadi; Ketabi, S. A.; Elahi, Seyed Mohammad; Sebt, S. A.

doi:10.1140/epjb/e2012-30056-8

Cited by 10 publications

(8 citation statements)

References 39 publications

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“…The Hamiltonian of isolated molecule can be described in terms of an extended SSH model:

\begin{array}{l} left & H_{mol} & = \sum_{j, σ} ({}, ((), ϵ_{j} + e V_{G}) d_{j, σ}^{+} d_{j, σ} - t_{j, j + 1} ((), d_{j + 1, σ}^{+} d_{j, σ} + h \cdot c)) \\ left & - \sum_{j, α} ({}, ϵ_{S} ((), d_{4 j - 3, σ}^{+} d_{4 j - 3, σ} + d_{4 j, σ}^{+} d_{4 j, σ}) + t_{S} ((), d_{4 j - 3, σ}^{+} d_{4 j, σ} + normalh \cdot normalc)) \\ left & + \frac{K_{0}}{2} \sum_{j} {((), u_{j + 1} - u_{j})}^{2}, \end{array}

where

t_{j, j + 1} = t_{0} - t_{1} cos (\frac{j π}{2}) - α (u_{j + 1} - u_{j}),

…”

Section: Model and Formalismmentioning

confidence: 99%

“…The input parameters in Equation are: zero displacement hopping integral t 0 , non‐degeneracy parameter t 1 , electron‐lattice coupling constant α , the elastic constant K 0 , and the lattice displacement at site j , u j . For obtaining of u j , the Schrödinger equation can be solved for the electronic part of Hamiltonian Equation to find the electronic eigenstate

| ψ_{μ, σ}⟩ = \sum_{i} ϕ_{i, μ, σ} d_{i, σ}^{†} | 0⟩

and eigenvalue ϵ μ,σ as follows:

\begin{array}{l} left & ϵ_{j} ϕ_{i, μ, σ} - t_{i, i + 1} ϕ_{i + 1, μ, σ} - t_{i, i - 1} ϕ_{i - 1, μ, σ} \\ left & - (ϵ_{s} ϕ_{i, μ, σ} + t_{s} ϕ_{i - 3, μ, σ}) Δ (\frac{i}{4}, int) \\ left & - (ϵ_{s} ϕ_{i, μ, σ} + t_{s} ϕ_{i + 3, μ, σ}) Δ (\frac{i - 3}{4}, int) = ϵ_{μ, σ} ϕ_{i, μ, σ}, \end{array}

where,

Δ (x, int) = \{\begin{array}{c} center & 1, & x = integer, \\ center & 0, & otherwise, \end{array}

…”

Section: Model and Formalismmentioning

confidence: 99%

“…[38] The input parameters in Equation (4) are: zero displacement hopping integral t 0 , non-degeneracy parameter t 1 , [39] electron-lattice coupling constant a, the elastic constant K 0 , and the lattice displacement at site j, u j . For obtaining of u j , the Schr€ odinger equation can be solved for the electronic part of Hamiltonian Equation (3) E and eigenvalue e m,s as follows: [36,37,40]…”

Section: Model and Formalismmentioning

confidence: 99%

See 2 more Smart Citations

Spin Thermoelectric Properties of Polythiophene Molecular Junction

Golsanamlou

Tagani

Soleimani

2014

Macro Theory & Simulations

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Spin thermoelectric properties of different lengths of polythiophene in molecular junction are investigated using Green function in linear response regime. An extended Su‐Schrieffer‐Heeger model is used to describe the Hamiltonian of the molecule. The coupling of molecular chain to three‐dimensional ferromagnetic electrodes is studied by a tight‐binding model for both parallel and antiparallel configurations. The decrease of HOMO‐LUMO gap and magnetothermopower and increase of oscillation of the spin thermopower and spin figure of merit are the most important phenomena observed by increasing the molecular length. In addition, results show that the spin thermoelectric coefficients are strongly related to the integral exchange energy.

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“…The Hamiltonian of isolated molecule can be described in terms of an extended SSH model:

\begin{array}{l} left & H_{mol} & = \sum_{j, σ} ({}, ((), ϵ_{j} + e V_{G}) d_{j, σ}^{+} d_{j, σ} - t_{j, j + 1} ((), d_{j + 1, σ}^{+} d_{j, σ} + h \cdot c)) \\ left & - \sum_{j, α} ({}, ϵ_{S} ((), d_{4 j - 3, σ}^{+} d_{4 j - 3, σ} + d_{4 j, σ}^{+} d_{4 j, σ}) + t_{S} ((), d_{4 j - 3, σ}^{+} d_{4 j, σ} + normalh \cdot normalc)) \\ left & + \frac{K_{0}}{2} \sum_{j} {((), u_{j + 1} - u_{j})}^{2}, \end{array}

where

t_{j, j + 1} = t_{0} - t_{1} cos (\frac{j π}{2}) - α (u_{j + 1} - u_{j}),

…”

Section: Model and Formalismmentioning

confidence: 99%

| ψ_{μ, σ}⟩ = \sum_{i} ϕ_{i, μ, σ} d_{i, σ}^{†} | 0⟩

and eigenvalue ϵ μ,σ as follows:

\begin{array}{l} left & ϵ_{j} ϕ_{i, μ, σ} - t_{i, i + 1} ϕ_{i + 1, μ, σ} - t_{i, i - 1} ϕ_{i - 1, μ, σ} \\ left & - (ϵ_{s} ϕ_{i, μ, σ} + t_{s} ϕ_{i - 3, μ, σ}) Δ (\frac{i}{4}, int) \\ left & - (ϵ_{s} ϕ_{i, μ, σ} + t_{s} ϕ_{i + 3, μ, σ}) Δ (\frac{i - 3}{4}, int) = ϵ_{μ, σ} ϕ_{i, μ, σ}, \end{array}

where,

Δ (x, int) = \{\begin{array}{c} center & 1, & x = integer, \\ center & 0, & otherwise, \end{array}

…”

Section: Model and Formalismmentioning

confidence: 99%

Section: Model and Formalismmentioning

confidence: 99%

See 1 more Smart Citation

Spin Thermoelectric Properties of Polythiophene Molecular Junction

Golsanamlou

Tagani

Soleimani

2014

Macro Theory & Simulations

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“…In the conventional spin-valve geometry, a non-magnetic spacer, which controls the total resistance of the device, the spin polarization and transport, is sandwiched between two magnetic contacts. Among many suggestions for possible non-magnetic spacers, organic materials provide desirable properties like flexibility, inexpensive material and production methods have attracted investigations in the organic electronics [1][2][3][4][5][6][7][8][9][10][11][12] . Besides, the spinorbit coupling and hyperfine interactions in the organic materials are very weak so that the spin memory can be as long as a few seconds.…”

Section: Introductionmentioning

confidence: 99%

Effects of impurity on tunnel magnetoresistance in a ferromagnetic electrode/carbon nanotube/ferromagnetic electrode junctio

Fouladi,

Vahedi,

Soleymani

2014

Preprint

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Effects of impurity on the spin-dependent transport in a single wall carbon nanotube spin-valve, as ferromagnetic electrode/carbon nanotube/ferromagnetic electrode model junction is numerically investigated. Using a generalized Green's function method and the Landauer-Büttiker formalism, the impurity conditions are determined by randomly substitution of carbon atoms in the honeycomb carbon nanotube lattice by nitrogen and boron atoms. We have found that transport characteristics, including the spin-dependent current and tunnel magnetoresistance are strongly influenced by the impurity effects. We think that the results of the present report could be useful for designing the future spintronic devices.

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“…In addition, the spin-orbit coupling and hyperfine interaction in the organic molecules are so weak that the length of spin-relaxation is long and spin-flip process during transport can be neglected [9,10]. As a result, the organic molecules are good candidates for spin-polarized transport applications in the molecular spintronics field [11][12][13][14][15][16]. Tunnel magnetoresistance (TMR) which is a consequence of spin-polarized tunneling is extensively studied nowadays due to the vast potential applications to the building of spintronic devices such as magnetic memories, sensors, switches, and spin diodes and transistors [17,18].…”

mentioning

confidence: 99%

Effects of Molecular Conformation on the Spin-Dependent Transport Through the FM/Biphenyl/FM Junction

Fouladi

2015

J Supercond Nov Magn

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Effects of conformation on the spin-dependent transport in a molecular spin-valve, as FM/biphenyl/FM model junction, in which a biphenyl molecule attached to ferromagnetic (FM) electrodes are numerically investigated. The work is based on a tight-binding Hamiltonian model within the framework of a generalized Green's function method and relies on the Landauer-Büttiker formalism as the basis for studying the spin-dependent transport properties of this system. We have found that transport characteristics, including the spin-dependent transmission function, current and tunnel magnetoresistance (TMR) are strongly influenced by the variation of twist angle between two phenyl rings. It is shown that the twist angle can alter the sign of the TMR from a positive to a negative value. We think that the results of the present report could be useful for designing the future molecular spintronic devices.

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Effects of dephasing on the spin-dependent currents and noise power in a molecular junction

Cited by 10 publications

References 39 publications

Spin Thermoelectric Properties of Polythiophene Molecular Junction

Spin Thermoelectric Properties of Polythiophene Molecular Junction

Effects of impurity on tunnel magnetoresistance in a ferromagnetic electrode/carbon nanotube/ferromagnetic electrode junctio

Effects of Molecular Conformation on the Spin-Dependent Transport Through the FM/Biphenyl/FM Junction

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