Paramita Dutta

Multi-terminal electron transport through single phenalenyl molecule: A theoretical study

Abstract We do parametric calculations to elucidate multi-terminal electron transport properties through a molecular system where a single phenalenyl molecule is attached to semi-infinite one-dimensional metallic leads. A formalism based on the Green’s function technique is used for the calculations while the model is described by tight-binding Hamiltonian. We explore the transport properties in terms of conductance, reflection probability as well as current–voltage characteristic. The most significant feature we articulate is that all these characteristics are very sensitive to the locations where the leads are connected and also the molecule-to-lead coupling strengths. The presence of other leads also has a remarkable effect on these transport properties. We study these phenomena for two-, three- and four-terminal molecular systems. Our numerical study may be utilized in designing tailor-made molecular electronic devices.

Integer quantum Hall effect in a lattice model revisited: Kubo formalism

We investigate numerically the integer quantum Hall effect (IQHE) in a two-dimensional square lattice with non-interacting electrons in presence of disorder and subjected to uniform magnetic field in a direction perpendicular to the lattice plane. We employ nearest-neighbor tight-binding Hamiltonian to describe the system, and obtain the longitudinal and transverse conductivities using Kubo formalism. The interplay between the magnetic field and disorder is also discussed. Our analysis may be helpful in studying IQHE in any discrete lattice model.

Positional dependence of energy gap on line defect in armchair graphene nanoribbons: Two-terminal transport and related issues

The characteristics of energy band spectrum of armchair graphene nanoribbons in the presence of line defect are analyzed within a simple non-interacting tight-binding framework. In metallic nanoribbons, an energy gap may or may not appear in the band spectrum depending on the location of the defect line, while in semiconducting ribbons, the gaps are customized, yielding the potential applicabilities of graphene nanoribbons in nanoscale electronic devices. With a more general model, we also investigate two-terminal electron transport using Greens function formalism.

Quantum transport in an array of mesoscopic rings: Effect of interface geometry

Abstract Electron transport properties are investigated in an array of mesoscopic rings, where each ring is threaded by a magnetic flux ϕ . The array is attached to two semi-infinite one-dimensional metallic electrodes, namely, source and drain, where the rings are considered either in series or in parallel configuration. A simple tight-binding model is used to describe the system and all the calculations are done based on the Green’s function formalism. Here, we present conductance–energy and current–voltage characteristics in terms of ring-to-electrode coupling strength, ring–electrode interface geometry and magnetic flux. Most interestingly it is observed that, typical current amplitude in an array of mesoscopic rings in the series configuration is much larger compared to that in parallel configuration of those rings. This feature is completely different from the classical analogy which may provide an important signature in designing nano-scale electronic devices.

Magnetic response in a zigzag carbon nanotube

Abstract Magnetic response of interacting electrons in a zigzag carbon nanotube threaded by a magnetic flux is investigated within a Hartree-Fock mean field approach. Following the description of energy spectra for both non-interacting and interacting cases we analyze the behavior of persistent current in individual branches of a nanotube. Our present investigation leads to a possibility of getting a filling-dependent metal-insulator transition in a zigzag carbon nanotube.

A renormalization group study of persistent current in a quasiperiodic ring

Abstract We propose a real-space renormalization group approach for evaluating persistent current in a multi-channel quasiperiodic Fibonacci tight-binding ring based on a Greens function formalism. Unlike the traditional methods, the present scheme provides a powerful tool for the theoretical description of persistent current with a very high degree of accuracy in large periodic and quasiperiodic rings, even in the micron scale range, which emphasizes the merit of this work.

Magneto-transport in a binary alloy ring

Abstract Magneto-transport properties are investigated in a binary alloy ring subjected to an Aharonov–Bohm (AB) flux ϕ within a single-band non-interacting tight-binding framework. In the first part, we expose analytically the behavior of persistent current in an isolated ordered binary alloy ring as functions of electron concentration N e and AB flux ϕ . While, in the second part of the Letter, we discuss electron transport properties through a binary alloy ring attached to two semi-infinite one-dimensional metallic electrodes. The effect of impurities is also analyzed. From our study we propose that under suitable choices of the parameter values the system can act as a p -type or an n -type semiconductor.

Electric field induced localization phenomena in a ladder network with superlattice configuration: Effect of backbone environment

Electric field induced localization properties of a tight-binding ladder network in presence of backbone sites are investigated. Based on Greens function formalism we numerically calculate two-terminal transport together with density of states for different arrangements of atomic sites in the ladder and its backbone. Our results lead to a possibility of getting multiple mobility edges which essentially plays a switching action between a completely opaque to fully or partly conducting region upon the variation of system Fermi energy, and thus, support in fabricating mesoscopic or DNA-based switching devices.

Magneto-transport in closed and open mesoscopic loop structures: A review

Magneto-transport properties in closed and open loop structures are carefully reviewed within a tight-binding formalism. A novel mesoscopic phenomenon where a non-vanishing current is observed in a conducting loop upon the application of an Aharonov-Bohm flux

Persistent current in an ordered-disordered separated cylinder

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