arXiv subjects

S. N. Karmakar

Publications and source records attributed to S. N. Karmakar.

At least 19 recordsLinked to original sources

arXiv2022

Graphene nanopore devices for DNA sequencing: A tight-binding model study

We present a tight-binding model study of a two-terminal graphene nanopore device for sequential determination of DNA bases. Using Green's function technique we investigate the changes in electronic transport properties of the device due to insertion of different nucleotides into the nanopore created within a zigzag graphene nanoribbon. First we try to characterise the device in static condition and then go for sequencing application by setting the bias across it to a specific voltage and then recording the characteristic current signals corresponding to each nucleotides of a translocating DNA. Our investigations show that graphene nanopores can certainly become very efficient and reliable for sequencing applications in future.

cond-mat.mes-hall↗

arXiv2016

Multiple mobility edges in a 1D Aubry chain with Hubbard interaction in presence of electric field: Controlled electron transport

Electronic behavior of a 1D Aubry chain with Hubbard interaction is critically analyzed in presence of electric field. Multiple energy bands are generated as a result of Hubbard correlation and Aubry potential, and, within these bands localized states are developed under the application of electric field. Within a tight-binding framework we compute electronic transmission probability and average density of states using Green's function approach where the interaction parameter is treated under Hartree-Fock mean field scheme. From our analysis we find that selective transmission can be obtained by tuning injecting electron energy, and thus, the present model can be utilized as a controlled switching device.

cond-mat.mes-hall↗

arXiv2016

Circulating persistent current and induced magnetic field in a fractal network

We present the overall conductance as well as the circulating currents in individual loops of a Sierpinski gasket (SPG) as we apply bias voltage via the side attached electrodes. SPG being a self-similar structure, its manifestation on loop currents and magnetic fields are examined in various generations of this fractal and it has been observed that for a given configuration of the electrodes, the physical quantities exhibit certain regularity as we go from one generation to another. Also a notable feature is the introduction of anisotropy in hopping causes an increase in magnitude of overall transport current. These features are a subject of interest in this article.

cond-mat.mes-hall↗

arXiv2016

Electronic transport in single-helical protein molecules: Effects of multiple charge conduction pathways and helical symmetry

We propose a tight-binding model to investigate electronic transport properties of single helical protein molecules incorporating both the helical symmetry and the possibility of multiple charge transfer pathways. Our study reveals that due to existence of both the multiple charge transfer pathways and helical symmetry, the transport properties are quite rigid under influence of envi- ronmental fluctuations which indicates that these biomolecules can serve as better alternatives in nanoelectronic devices than its other biological counterparts e.g., single-stranded DNA.

cond-mat.mes-hall↗

arXiv2016

Detection of basepair mismatches in DNA using graphene based nanopore device

We present an unique way to detect basepair mismatches in DNA leading to different epigenetic disorder by the method of nanopore sequencing. Based on a tight-binding formulation of graphene nanopore based device, using Greens function approach we measure the changes in the electronic transport properties of the device as we translocate a double-stranded DNA through the nanopore embeded in a zigzag graphene nanoribbon. In the present work we not only successfully detect the usual AT and GC pairs, but also a set of possible mismatches in the complementary base-pairing without any ambiguity. Our investigation shows that this device can also be used for reliable sequential detection of other biomolecules.

cond-mat.mes-hall↗

arXiv2015

Localization phenomena in a DNA double helix structure : A twisted ladder model

In this work we propose a model for DNA double helix within the tight-binding framework that incorporates the helicity of the molecules. We have studied localization properties of three DNAsequences,the periodic poly(dG)-poly(dC) and poly(dA)-poly(dT) sequences and the random ATGCsequence, all of which are coupled to backbone withrandom site energies representing the environmentalfluctuations. We observe that due to helicity of DNA, electron transport is greatly enhancedand there exists almost a disorder-strength independent critical value of the hopping integral, thataccounts for helicity of DNA, for which the electronic states become maximally extended. We havealso investigated the effect of backbone energetics on the transmission and I-V characteristics of DNA.

cond-mat.mes-hall↗

arXiv2015

Conformation dependent magnetotransport in a single handed helical geometry

Conformation dependent circular current is investigated in a single handed helical geometry in presence of magnetic flux $ϕ$ within a Hartree-Fock mean field approach. The helical model is described by a set of non-planar rings connected by some vertical bonds where each ring is formed by introducing a non-zero hopping between the atoms $a$ and $b$ as shown in Fig.1. By stretching and compressing the geometry, circular current can be regulated significantly and thus the system can be exploited to design current controlled device at the nano-scale level. The proximity effect between the atomic sites $a$ and $b$ is also discussed in detail which exhibits interesting results.

cond-mat.mes-hall↗

arXiv2015

Electronic Specific Heat of DNA: Effects of backbones and disorder

In this present work we report the results of our investigation on the electronic specific heat (ESH) of DNA molecule modelled within the tight-binding framework. We take four different DNA sequences ranging from periodic, quasi-periodic to random and studied both ESH and also the density of states to supplement our ESH results. The role of the backbone structure and the effectsof environment on ESH are discussed. We observe that irrespective of the sequences there is auniversal response of the ESH spectra for a given disorder. The nature of response of specific heaton backbone disorder is totally opposite in low and high temperature regimes.

cond-mat.mes-hall↗

arXiv2015

Conformation dependent electronic transport in a DNA double-helix

In this work we report the study of conformation dependent electronic transport properties of DNA double-helix within tight-binding framework including its helical symmetry. We have studied the changes in localization properties of DNA as we alter the number of stacked bases within a pitch of the double-helix keeping the total number of nucleotides in the DNA chain fixed. We take three DNA sequences, two of them are periodic and one is random and observe that localization length increases as we increase the radius of DNA double-helix i.e., number of nucleotides within a pitch. We have also investigated the effect of backbone energetic on the I-V response of the system and we find that in presence of helical symmetry, depending on the interplay of conformal variation and disorder strength DNA can be found in either metallic or semiconducting and even in an insulating phase, which in turn successfully explain all the experimental findings by a single model.

cond-mat.mes-hall↗

arXiv2014

Persistent charge and spin currents in a quantum ring using Green's function technique: Interplay between magnetic flux and spin-orbit interactions

We put forward a new approach based on Green's function formalism to evaluate precisely persistent charge and spin currents in an Aharonov-Bohm ring subjected to Rashba and Dresselhaus spin-orbit interactions. Unlike conventional methods our present scheme circumvents direct evaluation of eigenvalues and eigenstates of the system Hamiltonian to determine persistent currents which essentially reduces possible numerical errors, especially for larger rings. The interplay of Aharonov-Bohm flux and spin-orbit interactions in persistent charge and spin currents of quantum rings is analyzed in detail and our results lead to a possibility of estimating the strength of any one of the spin-orbit fields provided the other one is known. All these features are exactly invariant even in presence of impurities, and therefore, can be substantiated experimentally.

cond-mat.mes-hall↗

arXiv2014

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 Green's 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.

cond-mat.mes-hall↗

arXiv2013

Spin-orbit interaction induced spin selective transmission through a multi-terminal mesoscopic ring

Spin dependent transport in a multi-terminal mesoscopic ring is investigated in presence of Rashba and Dresselhaus spin-orbit interactions. Within a tight-binding framework we use a general spin density matrix formalism to evaluate all three components ($P_x$, $P_y$ and $P_z$) of the polarization vector associated with the charge current through the outgoing leads. It explores the dynamics of the spin polarization vector of current propagating through the system subjected to the Rashba and/or the Dresselhaus spin-orbit couplings. The sensitivity of the polarization components on the electrode-ring interface geometry is discussed in detail. Our present analysis provides an understanding of the coupled spin and electron transport in mesoscopic bridge systems.

cond-mat.mes-hall↗

arXiv2013

A renormalization group study of persistent current in a quasiperiodic ring

We propose a real-space renormalization group approach for evaluating persistent current in a multi-channel quasiperiodic fibonacci tight-binding ring based on a Green's 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.

cond-mat.mes-hall↗

arXiv2013

Magnetic-non-magnetic superlattice chain with external electric field: Spin transport and the selective switching effect

Based on Green's function formalism, the existence of multiple mobility edges in a one-dimensional magnetic-non-magnetic superlattice geometry in presence of external electric field is predicted, and, it leads to the possibility of getting a metal-insulator transition at multiple values of Fermi energy. The role of electric field on electron localization is discussed for different arrangements of magnetic and non-magnetic atomic sites in the chain. We also analyze that the model quantum system can be used as a perfect spin filter for a wide range of energy.

cond-mat.mes-hall↗

arXiv2013

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 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 Green's function formalism.

cond-mat.mes-hall↗

arXiv2012

Spin Hall effect in a Kagome lattice driven by Rashba spin-orbit interaction

Using four-terminal Landauer-Büttiker formalism and Green's function technique, in this present paper, we calculate numerically spin Hall conductance (SHC) and longitudinal conductance of a finite size kagome lattice with Rashba spin-orbit (SO) interaction both in presence and absence of external magnetic flux in clean limit. In the absence of magnetic flux, we observe that depending on the Fermi surface topology of the system SHC changes its sign at different values of Fermi energy, along with the band center. Unlike the infinite system (where SHC is a universal constant $\pm \frac{e}{8 π}$), here SHC depends on the external parameters like SO coupling strength, Fermi energy, etc. We show that in the presence of any arbitrary magnetic flux, periodicity of the system is lost and the features of SHC tends to get reduced because of elastic scattering. But again at some typical values of flux ($ϕ=1/2, 1/4, 3/4..., etc.) the system retains its periodicity depending on its size and the features of spin Hall effect (SHE) reappears. Our predicted results may be useful in providing a deeper insight into the experimental realization of SHE in such geometries.

cond-mat.mes-hall↗

arXiv2012

Magneto-transport in a quantum network: Evidence of a mesoscopic switch

We investigate magneto-transport properties of a $θ$ shaped three-arm mesoscopic ring where the upper and lower sub-rings are threaded by Aharonov-Bohm fluxes $ϕ_1$ and $ϕ_2$, respectively, within a non-interacting electron picture. A discrete lattice model is used to describe the quantum network in which two outer arms are subjected to binary alloy lattices while the middle arm contains identical atomic sites. It is observed that the presence of the middle arm provides localized states within the band of extended regions and lead to the possibility of switching action from a high conducting state to a low conducting one and vice versa. This behavior is justified by studying persistent current in the network. Both the total current and individual currents in three separate branches are computed by using second-quantized formalism and our idea can be utilized to study magnetic response in any complicated quantum network. The nature of localized eigenstates are also investigated from probability amplitudes at different sites of the quantum device.

cond-mat.mes-hall↗

arXiv2012

Magneto-transport in a binary alloy ring

Magneto-transport properties are investigated in a binary alloy ring subjected to an Aharonov-Bohm (AB) flux ϕwithin 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 article, 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.

cond-mat.mes-hall↗