arXiv subjects

Santanu K. Maiti

Publications and source records attributed to Santanu K. Maiti.

At least 145 records · Page 8Linked to original sources

arXiv2009

Quantum transport in honeycomb lattice ribbons with zigzag edges: A theoretical study

We explore electron transport properties in honeycomb lattice ribbons with zigzag edges coupled to two semi-infinite one-dimensional metallic electrodes. The calculations are based on the tight-binding model and the Green's function method, which numerically compute the conductance-energy and current-voltage characteristics as functions of the lengths and widths of the ribbons. Our numerical results predict that for such a ribbon an energy gap always appears in the conductance spectrum across the energy E=0. With the increase of the size of the ribbon, the gap gradually decreases but it never vanishes. This clearly manifests that a honeycomb lattice ribbon with zigzag edges always exhibits the semiconducting behavior, and it becomes much more clearly visible from our presented current-voltage characteristics.

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arXiv2009

Quantum transport through a molecule coupled to a mesoscopic ring: A theoretical study

Transport through a molecule sandwiched between two metallic electrodes and coupled to a mesoscopic ring that threads a magnetic flux $ϕ$ is studied. An analytic approach for the electron transport through the molecular bridge system is presented. Electronic transport properties are discussed in two aspects: (a) presence of external magnetic filed and (b) strength of molecule-to-electrode coupling.

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arXiv2009

Tuning of electron transport through a quantum wire: An exact study

We explore electron transport properties in a quantum wire attached to two metallic electrodes. A simple tight-binding model is used to describe the system and the coupling of the wire to the electrodes (source and drain) is treated through Newns-Anderson chemisorption theory. In our present model, the site energies of the wire are characterized by the relation $ε_i=W\cos(i λ^νπ)$ where $W$, $λ$, $ν$ are three positive numbers. For $ν=0$, the threshold bias voltage of electron conduction across the bridge can be controlled very nicely by tuning the strength of the potential $W$. On the other hand, for $ν\ne 0$, the wire becomes an aperiodic one and quite interestingly we see that, for some special values of $ν$, the system exhibits a {\em metal-insulator} transition which provides a significant feature in this particular study. Our numerical results may be useful for fabrication of efficient switching devices.

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arXiv2009

Magnetic Quantum Wire as a Spin Filter: An Exact Study

We propose that a magnetic quantum wire composed of magnetic and non-magnetic atomic sites can be used as a spin filter for a wide range of applied bias voltage. We adopt a simple tight-binding Hamiltonian to describe the model where the quantum wire is attached to two semi-infinite one-dimensional non-magnetic electrodes. Based on single particle Green's function formalism all the calculations are performed numerically which describe two-terminal conductance and current through the wire. Our exact results may be helpful in fabricating mesoscopic or nano-scale spin filter.

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arXiv2009

Implementation of Nano-scale Rectifiers: An Exact Study

We propose the possibilities of designing nano-scale rectifiers using mesoscopic rings. A single mesoscopic ring is used for half-wave rectification, while full-wave rectification is achieved using two such rings and in both cases each ring is threaded by a time varying magnetic flux $ϕ$ which plays a central role in the rectification action. Within a tight-binding framework, all the calculations are done based on the Green's function formalism. We present numerical results for the two-terminal conductance and current which support the general features of half-wave and full-wave rectifications. The analysis may be helpful in fabricating mesoscopic or nano-scale rectifiers.

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arXiv2009

Quantum Transport through Organic Molecules

We explore electron transport properties for the model of benzene-1, 4-dithiolate (BDT) molecule and for some other geometric models of benzene molecule attached to two semi-infinite one-dimensional metallic electrodes using the Green's function formalism. An analytic approach, based on a simple tight-binding framework, is presented to describe electron transport through the molecular wires. Electronic transport in such molecular systems is strongly affected by the geometry of the molecules as well as their coupling to the side-attached electrodes. Conductance reveals resonant peaks associated with the molecular energy eigenstates providing several complex spectra. Current passing through the molecules shows staircase-like behavior with sharp steps in the weak molecule-to-electrode coupling limit, while it varies quite continuously with the applied bias voltage in the limit of strong molecular coupling. In the presence of transverse magnetic field, conductance exhibits oscillatory behavior with flux $ϕ$, threaded by the molecular ring, showing $ϕ_0$ ($=ch/e$) flux-quantum periodicity. Though, conductance changes in the presence of transverse magnetic field, but the current-voltage characteristics are not significantly affected by this field.

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arXiv2009

Quantum transport through polycyclic hydrocarbon molecules: Green's function approach

Quantum transport properties through single polycyclic hydrocarbon molecules attached to two metallic electrodes are studied by the use of Green's function technique. A parametric approach based on the tight-binding model is introduced to investigate the electronic transport through such molecular bridge systems. The transport properties are discussed in the aspects of (a) molecule-to-electrode coupling strength and (b) quantum interference effect.

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arXiv2009

NOT gate response in a mesoscopic ring: An exact result

We explore NOT gate response in a mesoscopic ring threaded by a magnetic flux $ϕ$. The ring is attached symmetrically to two semi-infinite one-dimensional metallic electrodes and a gate voltage, viz, $V_a$, is applied in one arm of the ring which is treated as the input of the NOT gate. The calculations are based on the tight-binding model and the Green's function method, which numerically compute the conductance-energy and current-voltage characteristics as functions of the ring-to-electrodes coupling strength, magnetic flux and gate voltage. Our theoretical study shows that, for $ϕ=ϕ_0/2$ ($ϕ_0=ch/e$, the elementary flux-quantum) a high output current (1) (in the logical sense) appears if the input to the gate is low (0), while a low output current (0) appears when the input to the gate is high (1). It clearly exhibits the NOT gate behavior and this aspect may be utilized in designing an electronic logic gate.

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arXiv2009

Multi-terminal quantum transport through a single benzene molecule: Evidence of a Molecular Transistor

We explore multi-terminal quantum transport through a benzene molecule threaded by an Aharonov-Bohm flux $ϕ$. A simple tight-binding model is used to describe the system and all the calculations are done based on the Green's function formalism. With a brief description of two-terminal quantum transport, we present a detailed study of three-terminal transport properties through the benzene molecule to reveal the actual mechanism of electron transport. Here we numerically compute the multi-terminal conductances, reflection probabilities and current-voltage characteristics in the aspects of molecular coupling strength and magnetic flux $ϕ$. Most significantly we observe that, the molecular system where the benzene molecule is attached to three terminals can be operated as a transistor, and we call it a molecular transistor. This aspect can be utilized in designing nano-electronic circuits and our investigation may provide a basic framework to study electron transport in any complicated multi-terminal quantum system.

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arXiv2009

Electron transport through a quantum interferometer with side-coupled quantum dots: Green's function approach

We study electron transport through a quantum interferometer with side-coupled quantum dots. The interferometer, threaded by a magnetic flux $ϕ$, is attached symmetrically to two semi-infinite one-dimensional metallic electrodes. The calculations are based on the tight-binding model and the Green's function method, which numerically compute the conductance-energy and current-voltage characteristics. Our results predict that under certain conditions this particular geometry exhibits anti-resonant states. These states are specific to the interferometric nature of the scattering and do not occur in conventional one-dimensional scattering problems of potential barriers. Most importantly we show that, such a simple geometric model can also be used as a classical XOR gate, where the two gate voltages, viz, $V_a$ and $V_b$, are applied, respectively, in the two dots those are treated as the two inputs of the XOR gate. For $ϕ=ϕ_0/2$ ($ϕ_0=ch/e$, the elementary flux-quantum), a high output current (1) (in the logical sense) appears if one, and only one, of the inputs to the gate is high (1), while if both inputs are low (0) or both are high (1), a low output current (0) appears. It clearly demonstrates the XOR gate behavior and this aspect may be utilized in designing the electronic logic gate.

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arXiv2009

Quantum transport in a mesoscopic ring: Evidence of an OR gate

We explore OR gate response in a mesoscopic ring threaded by a magnetic flux $ϕ$. The ring is symmetrically attached to two semi-infinite one-dimensional metallic electrodes and two gate voltages, viz, $V_a$ and $V_b$, are applied in one arm of the ring which are treated as the two inputs of the OR gate. All the calculations are based on the tight-binding model and the Green's function method, which numerically compute the conductance-energy and current-voltage characteristics as functions of the gate voltages, ring-to-electrodes coupling strengths and magnetic flux. Our theoretical study shows that, for $ϕ=ϕ_0/2$ ($ϕ_0=ch/e$, the elementary flux-quantum) a high output current (1) (in the logical sense) appears if one or both the inputs to the gate are high (1), while if neither input is high (1), a low output current (0) appears. It clearly demonstrates the OR gate behavior and this aspect may be utilized in designing the electronic logic gate.

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arXiv2009

NOR gate response in a double quantum ring: An exact result

NOR gate response in a double quantum ring, where each ring is threaded by a magnetic flux $ϕ$, is investigated. The double quantum ring is sandwiched symmetrically between two semi-infinite one-dimensional metallic electrodes and two gate voltages, namely, $V_a$ and $V_b$, are applied, respectively, in lower arms of the two rings those are treated as the two inputs of the NOR gate. A simple tight-binding model is used to describe the system and all the calculations are done through the Green's function formalism. Here we exactly calculate the conductance-energy and current-voltage characteristics as functions of the ring-to-electrode coupling strengths, magnetic flux and gate voltages. Our numerical study predicts that, for a typical value of the magnetic flux $ϕ=ϕ_0/2$ ($ϕ_0=ch/e$, the elementary flux-quantum), a high output current (1) (in the logical sense) appears if both the inputs to the gate are low (0), while if one or both are high (1), a low output current (0) results. It clearly demonstrates the NOR gate behavior and this aspect may be utilized in designing an electronic logic gate.

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arXiv2009

NAND gate response in a mesoscopic ring: An exact study

NAND gate response in a mesoscopic ring threaded with a magnetic flux $ϕ$ is investigated by using Green's function formalism. The ring is attached symmetrically to two semi-infinite one-dimensional metallic electrodes and two gate voltages, namely, $V_a$ and $V_b$, are applied in one arm of the ring those are treated as the two inputs of the NAND gate. We use a simple tight-binding model to describe the system and numerically compute the conductance-energy and current-voltage characteristics as functions of the gate voltages, ring-to-electrode coupling strength and magnetic flux. Our theoretical study shows that, for $ϕ=ϕ_0/2$ ($ϕ_0=ch/e$, the elementary flux-quantum) a high output current (1) (in the logical sense) appears if one or both the inputs to the gate are low (0), while if both the inputs to the gate are high (1), a low output current (0) appears. It clearly exhibits the NAND gate behavior and this feature may be utilized in designing an electronic logic gate.

cond-mat.mes-hall↗

arXiv2009

Electron transport in a double quantum ring: Evidence of an AND gate

We explore AND gate response in a double quantum ring where each ring is threaded by a magnetic flux $ϕ$. The double quantum ring is attached symmetrically to two semi-infinite one-dimensional metallic electrodes and two gate voltages, namely, $V_a$ and $V_b$, are applied, respectively, in the lower arms of the two rings which are treated as two inputs of the AND gate. The system is described in the tight-binding framework and the calculations are done using the Green's function formalism. Here we numerically compute the conductance-energy and current-voltage characteristics as functions of the ring-to-electrode coupling strengths, magnetic flux and gate voltages. Our study suggests that, for a typical value of the magnetic flux $ϕ=ϕ_0/2$ ($ϕ_0=ch/e$, the elementary flux-quantum) a high output current (1) (in the logical sense) appears only if both the two inputs to the gate are high (1), while if neither or only one input to the gate is high (1), a low output current (0) results. It clearly demonstrates the AND gate behavior and this aspect may be utilized in designing an electronic logic gate.

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arXiv2009

XOR gate response in a mesoscopic ring with embedded quantum dots

We address XOR gate response in a mesoscopic ring threaded by a magnetic flux $ϕ$. The ring, composed of identical quantum dots, is symmetrically attached to two semi-infinite one-dimensional metallic electrodes and two gate voltages, viz, $V_a$ and $V_b$, are applied, respectively, in each arm of the ring which are treated as the two inputs of the XOR gate. The calculations are based on the tight-binding model and the Green's function method, which numerically compute the conductance-energy and current-voltage characteristics as functions of the ring-electrodes coupling strengths, magnetic flux and gate voltages. Quite interestingly it is observed that, for $ϕ=ϕ_0/2$ ($ϕ_0=ch/e$, the elementary flux-quantum) a high output current (1) (in the logical sense) appears if one, and only one, of the inputs to the gate is high (1), while if both inputs are low (0) or both are high (1), a low output current (0) appears. It clearly demonstrates the XOR behavior and this aspect may be utilized in designing the electronic logic gate.

cond-mat.mes-hall↗

arXiv2009

A mesoscopic ring as a XNOR gate: An exact result

We describe XNOR gate response in a mesoscopic ring threaded by a magnetic flux $ϕ$. The ring is attached symmetrically to two semi-infinite one-dimensional metallic electrodes and two gate voltages, viz, $V_a$ and $V_b$, are applied in one arm of the ring which are treated as the inputs of the XNOR gate. The calculations are based on the tight-binding model and the Green's function method, which numerically compute the conductance-energy and current-voltage characteristics as functions of the ring-to-electrode coupling strength, magnetic flux and gate voltages. Our theoretical study shows that, for a particular value of $ϕ$ ($=ϕ_0/2$) ($ϕ_0=ch/e$, the elementary flux-quantum), a high output current (1) (in the logical sense) appears if both the two inputs to the gate are the same, while if one but not both inputs are high (1), a low output current (0) results. It clearly exhibits the XNOR gate behavior and this aspect may be utilized in designing an electronic logic gate.

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arXiv2009

Electron transport in polycyclic hydrocarbon molecules: A study of shot noise contribution to the power spectrum

We study electron transport in polycyclic hydrocarbon molecules attached to two semi-infinite one-dimensional metallic electrodes by the use of Green's function formalism. Parametric calculations based on the tight-binding framework are given to investigate the transport properties through such molecular bridges. In this context we also discuss noise power of current fluctuations and focus our attention on the shot noise contribution to the power spectrum. The electron transport properties are significantly influenced by (a) length of the molecule, (b) molecule-electrode interface geometry and (c) molecular coupling strength to the electrodes.

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arXiv2009

Quantum transport through a conducting bridge: Correlation between surface disorder and bulk disorder

We explore a novel transport phenomenon by studying the effect of surface disorder on electron transport through a finite size conductor with side coupled metallic electrodes. In the strong disorder regime the current amplitude increases with the increase of the surface disorder strength, while, the amplitude decreases in the weak disorder regime. This behavior is completely opposite to that of bulk disordered system. In this article we also investigate the effects of the size of the conductor and the transverse magnetic field on electron transport and see that the transport properties are significantly influenced by them.

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