Santanu K. Maiti

Quantum transport through polycyclic hydrocarbon molecules

Quantum transport properties through single polycyclic hydrocarbon molecules sandwiched between two metallic electrodes are studied by the use of Greens function technique. Here we introduce parametric approach, based on the tight-binding model to investigate the electronic transport through such molecular bridge systems. The electronic transport properties are discussed in two aspects: (a) the molecule-to-electrodes coupling strength and (b) the quantum interference effect.

Effect of dephasing on electron transport in a molecular wire: Green’s function approach

Abstract The effect of dephasing on electron transport through a benzene molecule is carefully examined using a phenomenological model introduced by Buttiker. Within a tight-binding framework all the calculations are performed based on the Green’s function formalism. We investigate the influence of dephasing on transmission probability and current–voltage characteristics for three different configurations ( ortho , meta and para ) of the molecular system depending on the locations of two contacting leads. The presence of dephasing provides a significant change in the spectral properties of the molecule and exhibits several interesting patterns that have so far remain unexplored.

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

Abstract 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 Greens 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 = c h / 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.

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

Abstract We study electron transport characteristics through some polycyclic hydrocarbon molecules attached with two metallic electrodes by the use of Green’s function technique. Here we do parametric calculations based on the tight-binding model to investigate the transport properties through such molecular bridges. In this context we also discuss noise power of the current fluctuations and focus our attention on the shot noise contribution to the power spectrum. The electron transport characteristics are significantly influenced by (a) the length of the molecules, (b) the interference effects and (c) the molecule-to-electrodes coupling strength.

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

Abstract 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 calculate exactly 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 = c h / 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.

Electron transport through mesoscopic ring

The quantum transport properties of a non-interacting mesoscopic ring sandwiched between two metallic electrodes are investigated by the use of Greens function technique. Here, we introduce parametric approach, based on the tight-binding model to study these transport properties. The electronic transport properties are focused in three aspects: (a) geometry of the mesoscopic ring, (b) coupling strength of the ring with the two electrodes and (c) magnetic flux threaded by the ring.

Effect of localizing groups on quantum transport through single conjugated molecules

Quantum transport through single conjugated molecules sandwiched between two non-superconducting electrodes is studied by the use of Greens 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-electrodes coupling strength and here we focus our results in these two aspects.

Magneto-transport in a mesoscopic ring with Rashba and Dresselhaus spin-orbit interactions

Electronic transport in a one-dimensional mesoscopic ring threaded by a magnetic flux is studied in the presence of Rashba and Dresselhaus spin-orbit interactions. A completely analytical technique within a tight-binding formalism unveils the spin-split bands in the presence of the spin-orbit interactions and leads to a method of determining the strength of the Dresselhaus interaction. In addition to this, the persistent currents for ordered and disordered rings have been investigated numerically. It is observed that the presence of the spin-orbit interaction, in general, leads to an enhanced amplitude of the persistent current. Numerical results corroborate the respective analytical findings.

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.

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

Abstract We explore the 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, V a and V b , are applied in one arm of the ring; these 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-electrode coupling strengths and magnetic flux. Our theoretical study shows that, for ϕ = ϕ 0 / 2 ( ϕ 0 = c h / 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 an electronic logic gate.