arXiv subjects

Santanu K. Maiti

Publications and source records attributed to Santanu K. Maiti.

At least 163 records · Page 9Linked to original sources

arXiv2009

Electronic transport in a mesoscopic ring

Electron transport properties of a non-interacting mesoscopic ring sandwiched between two metallic electrodes are investigated by the use of Green's function formalism. We introduce a parametric approach based on the tight-binding model to study the transport properties. The electronic transport characteristics are investigated in three aspects: (a) ring-electrode interface geometry, (b) coupling strength of the ring to the electrodes and (c) magnetic flux threaded by the ring.

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arXiv2009

Electron transport through multilevel quantum dot

Quantum transport properties through some multilevel quantum dots sandwiched between two metallic contacts are investigated by the use of Green's function technique. Here we do parametric calculations, based on the tight-binding model, to study the transport properties through such bridge systems. The electron transport properties are significantly influenced by (a) number of quantized energy levels in the dots, (b) dot-to-electrode coupling strength, (c) location of the equilibrium Fermi energy $E_F$ and (d) surface disorder. In the limit of weak-coupling, the conductance ($g$) shows sharp resonant peaks associated with the quantized energy levels in the dots, while, they get substantial broadening in the strong-coupling limit. The behavior of the electron transfer through these systems becomes much more clearly visible from our study of current-voltage ($I$-$V$) characteristics. In this context we also describe the noise power of current fluctuations ($S$) and determine the Fano factor ($F$) which provides an important information about the electron correlation among the charge carriers. Finally, we explore a novel transport phenomenon by studying the surface disorder effect in which the current amplitude increases with the increase of the surface disorder strength in the strong disorder regime, while, the amplitude decreases in the limit of weak disorder. Such an anomalous behavior is completely opposite to that of bulk disordered system where the current amplitude always decreases with the disorder strength. It is also observed that the current amplitude strongly depends on the system size which reveals the finite quantum size effect.

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arXiv2009

Quantum transport through single phenalenyl molecule: Effect of interface structure

Electronic transport characteristics through a single phenalenyl molecule sandwiched between two metallic electrodes are investigated by the use of Green's function technique. A parametric approach, based on the tight-binding model, is used to study the transport characteristics through such molecular bridge system. The electronic transport properties are significantly influenced by (a) the molecule-to-electrode interface structure and (b) the molecule-to-electrode coupling strength.

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arXiv2009

Tuning of electron transport through a moebius strip: shot noise

We explore electron transport through a moebius strip attached to two metallic electrodes by the use of Green's function technique. A parametric approach is used based on the tight-binding model to characterize the electron transport through such a bridge system and it is observed that the transport properties are significantly affected by (a) the transverse hopping strength between the two channels and (b) the strip-to-electrode coupling strength. In this context we also describe the noise power of the current fluctuations that provides a key information about the electron correlation which is obtained by calculating the Fano factor ($F$). The knowledge of this current fluctuations gives important ideas for fabrication of efficient electronic devices.

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arXiv2009

Molecular wires: tuning of electron transport

Electron transport characteristics through molecular wires are studied by using the Green's function formalism. Parametric calculations are performed based on the tight-binding model to investigate the transport properties through the wires. The transport characteristics are significantly influenced by (a) the interference effects, (b) chemical substituent group, (c) molecule-to-electrode coupling strength and (d) the gate voltage, and, here we focus our results in these aspects. In this article we also discuss the noise power of current fluctuations. The noise power gives key information about the electron correlation which is obtained by calculating the Fano factor (F) and the complete knowledge of the current fluctuations is very essential to fabricate efficient molecular devices.

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arXiv2009

Electron transport through a quantum wire coupled with a mesoscopic ring

Electronic transport through a quantum wire sandwiched between two metallic electrodes and coupled to a quantum ring, threaded by a magnetic flux $ϕ$, is studied. An analytic approach for the electron transport through the bridge system is presented based on the tight-binding model. The transport properties are discussed in three aspects: (a) presence of an external magnetic filed, (b) strength of the wire to electrode coupling, and (c) presence of in-plane electric field.

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arXiv2009

Effect of localizing groups on electron transport through single conjugated molecules

Electron transport properties through single conjugated molecules sandwiched between two non-superconducting electrodes are studied by the use of Green's function technique. Based on the tight-binding model, we do parametric calculations to characterize the electron transport through such molecular bridges. The electron transport properties are significantly influenced by (a) the existence of localizing groups in these conjugated molecules and (b) the molecule to electrode coupling strength, and, here we focus our results in these two aspects.

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arXiv2009

Strange effect of disorder on electron transport through a thin film

A novel feature of electron transport is explored through a thin film of varying impurity density with the distance from its surface. The film, attached to two metallic electrodes, is described by simple tight-binding model and its coupling to the electrodes is treated through Newns-Anderson chemisorption theory. Quite interestingly it is observed that, in the strong disorder regime the amplitude of the current passing through the film increases with the increase of the disorder strength, while it decreases in the weak disorder regime. This anomalous behavior is completely opposite to that of conventional disordered systems. Our results also predict that the electron transport is significantly influenced by the finite size of the thin film.

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arXiv2009

Effect of isomers on quantum transport through molecular bridge system

Quantum transport for different models of isomer molecules attached to two semi-infinite leads is studied on the basis of Green's function technique. Electronic transport properties are significantly affected by (a) the relative position of the atoms in these molecules and (b) the molecule-to-lead coupling strength of these molecular bridge systems.

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arXiv2009

Anomalous Quantum Diffusion in Order-Disorder Separated Double Quantum Ring

A novel feature for control of carrier mobility is explored in an order-disorder separated double quantum ring, where the two rings thread different magnetic fluxes. Here we use simple tight-binding formulation to describe the system. In our model, the two rings are connected through a single bond and one of the rings is subjected to impurity, keeping the other ring as impurity free. In the strong impurity regime, the electron diffusion length increases with the increase of the impurity strength, while it decreases in the weak impurity regime. This phenomenon is completely opposite to that of a conventional disordered double quantum ring, where the electron diffusion length always decreases with the increase of the disorder strength.

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arXiv2009

Persistent current and low-field magnetic susceptibility in one-dimensional mesoscopic rings: Effect of long-range hopping

Persistent current and low-field magnetic susceptibility in single-channel normal metal rings threaded by a magnetic flux $ϕ$ are investigated within the tight-binding framework considering long-range hopping of electrons in the {\em shortest} path. The higher order hopping integrals try to reduce the effect of disorder by delocalizing the energy eigenstates, and accordingly, current amplitude in disordered rings becomes comparable to that of an ordered ring. Our study of low-field magnetic susceptibility predicts that the sign of persistent currents can be mentioned precisely in mesoscopic rings with fixed number of electrons, even in the presence of impurity in the rings. For perfect rings, low-field current shows only the diamagnetic sign irrespective of the total number of electrons $N_e$. On the other hand, in disordered rings it exhibits the diamagnetic and paramagnetic natures for the rings with odd and even $N_e$ respectively.

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arXiv2009

Quantum transport through molecular wires

We explore electron transport properties in molecular wires made of heterocyclic molecules (pyrrole, furan and thiophene) by using the Green's function technique. Parametric calculations are given based on the tight-binding model to describe the electron transport in these wires. It is observed that the transport properties are significantly influenced by (a) the heteroatoms in the heterocyclic molecules and (b) the molecule-to-electrodes coupling strength. Conductance ($g$) shows sharp resonance peaks associated with the molecular energy levels in the limit of weak molecular coupling, while they get broadened in the strong molecular coupling limit. These resonances get shifted with the change of the heteroatoms in these heterocyclic molecules. All the essential features of the electron transfer through these molecular wires become much more clearly visible from the study of our current-voltage ($I$-$V$) characteristics, and they provide several key informations in the study of molecular transport.

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arXiv2009

Quantum Transport in a Biphenyl Molecule: Effects of Magnetic Flux

Electron transport properties of a biphenyl molecule are studied based on the Green's function formalism. The molecule is sandwiched between two metallic electrodes, where each benzene ring is threaded by a magnetic flux $ϕ$. The results are focused on the effects of the molecule to electrode coupling strength and the magnetic flux $ϕ$. Our numerical study shows that, for a fixed molecular coupling, the current amplitude across the bridge can be {\em regulated} significantly just by tuning the flux $ϕ$. This aspect may be utilized in designing nano-scale electronic circuits.

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arXiv2009

Electron transport through molecular bridge systems

Electron transport characteristics are investigated through some molecular chains attached to two non-superconducting electrodes by the use of Green's function method. Here we do parametric calculations based on the tight-binding formulation to characterize the electron transport through such bridge systems. The transport properties are significantly influenced by (a) the length of the molecular chain and (b) the molecule-to-electrodes coupling strength and here we focus are results in these aspects. In this context we also discuss the steady state current fluctuations, the so-called shot noise, which is a consequence of the quantization of charge and is not directly available through conductance measurements.

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arXiv2009

Quantum Transport in Bridge Systems

We study electron transport properties of some molecular wires and a unconventional disordered thin film within the tight-binding framework using Green's function technique. We show that electron transport is significantly affected by quantum interference of electronic wave functions, molecule-to-electrode coupling strengths, length of the molecular wire and disorder strength. Our model calculations provide a physical insight to the behavior of electron conduction across a bridge system.

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arXiv2009

Persistent current in a mesoscopic cylinder: effects of radial magnetic field

In this work, we study persistent current in a mesoscopic cylinder subjected to both longitudinal and transverse magnetic fluxes. A simple tight-binding model is used to describe the system, where all the calculations are performed exactly within the non-interacting electron picture. The current $I$ is investigated numerically concerning its dependence on total number of electrons $N_e$, system size $N$, longitudinal magnetic flux $ϕ_l$ and transverse magnetic flux $ϕ_t$. Quite interestingly we observe that typical current amplitude oscillates as a function of the transverse magnetic flux, associated with the energy-flux characteristics, showing $N ϕ_0$ flux-quantum periodicity, where $N$ and $ϕ_0$ $(=ch/e)$ correspond to the system size and the elementary flux-quantum respectively. This analysis may provide a new aspect of persistent current for multi-channel cylindrical systems in the presence of radial magnetic field $B_r$, associated with the flux $ϕ_t$.

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arXiv2009

Magnetic field controlled electron transport in a thin cylinder

We explore electron transport in a thin cylinder, attached to two semi-infinite one-dimensional metallic electrodes, in the presence of both longitudinal and transverse magnetic fluxes. A simple tight-binding model is used to describe the system, where all the calculations are performed in the Green's function formalism. Quite surprisingly it is observed that, typical current amplitude oscillates as a function of the transverse magnetic flux, associated with conductance-energy characteristics, showing $Nϕ_0$ flux-quantum periodicity, where $N$ and $ϕ_0$ $(=ch/e)$ correspond to the system size and elementary flux-quantum respectively. The analysis might be helpful in fabricating mesoscopic switching devices, where a particular response can be delayed by tuning the system size $N$.

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arXiv2009

Flux induced semiconducting behavior of a quantum network

We show that a diamond shaped periodic network, recently proposed as a model of a spin filter (A. Aharony {\em et al.} \cite{aharon08}) is capable of behaving as a p-type or an n-type semiconductor depending on a suitable choice of the on-site potentials of the atoms occupying the vertices of the lattice, and the strength of the magnetic flux threading each plaquette of the network. A detailed study of the density of states of an infinite network is made together with the conductance of finite sized system to establish the idea.

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