arXiv subjects

Santanu K. Maiti

Publications and source records attributed to Santanu K. Maiti.

At least 55 records · Page 3Linked to original sources

arXiv2024

Enhancing thermoelectric performance of 2D Janus ISbTe by strain engineering: A first principle study

Recent developments in the 2D materials laid emphasis on finding the materials with robust properties for variety of applications including the energy harvesting. The recent discovery of Janus monolayers with broken symmetry has opened up new options for engineering the properties of 2D layered materials. Present study focuses on enhancing thermoelectric properties of 2H-ISbTe 2D Janus monolayer. All the calculations have been performed using fully relaxed unit cell and employing the pseudo potential based quantum espresso code. Calculated structural parameters are in good agreement with previous literature reports. The lattice dynamics calculations predicts this monolayer can withstand a strain of up to 4% beyond which imaginary frequencies appear in the phonon dispersion curves. Computed electronic structure reveals that the monolayer is an indirect wide bandgap material and the bandgap decreases with tensile strain. Furthermore, the computed thermoelectric properties show that the studied monolayer has high Seebeck coefficient of ~ 300 μV/K and low thermal conductivity which yields reasonably high ZT of ~ 1.31 for a strain of 2% at 300 K with p-type doping. Therefore, our study signifies the fact that tensile strain and p-type doping of 2D Janus monolayer ISbTe can enhance ZT from 0.87 to 1.31 at room temperature which makes it a promising candidate for thermoelectric applications.

cond-mat.mtrl-sci↗

arXiv2024

Bias induced circular current in a loop nanojunction with AAH modulation: Role of hopping dimerization

In this work, we put forward, for the first time, the interplay between correlated disorder and hopping dimerization on bias driven circular current in a loop conductor that is clamped between two electrodes. The correlated disorder is introduced in site energies of the ring in the form of Aubry-André-Harper (AAH) model. Simulating the quantum system within a tight-binding framework all the results are worked out based on the standard wave-guide theory. Unlike transport current, commonly referred to drain current, circular current in the loop conductor can get enhanced with increasing disorder strength. This enhancement becomes much effective when hopping dimerization is included which is taken following the Su-Schrieffer-Heeger (SSH) model. The characteristic features of bias driven circular current are studied under different input conditions and we find the results are robust for wide range of physical parameters. Our analysis may provide a new insight in analyzing transport behavior in different disordered lattices in presence of additional restrictions in hopping integrals.

cond-mat.mes-hall↗

arXiv2023

Phenomenon of multiple reentrant localization in a double-stranded helix with transverse electric field

The present work explores the potential for observing multiple reentrant localization behavior in a double-stranded helical (DSH) system, extending beyond the conventional nearest-neighbor hopping interaction. The DSH system is considered to have hopping dimerization in each strand, while also being subjected to a transverse electric field. The inclusion of an electric field serves the dual purpose of inducing quasiperiodic disorder and strand-wise staggered site energies. Two reentrant localization regions are identified: one exhibiting true extended behavior in the thermodynamic limit, while the second region shows quasi-extended characteristics with partial spreading within the helix. The DSH system exhibits three distinct single-particle mobility edges linked to localization transitions present in the system. The analysis in this study involves examining various parameters such as the single-particle energy spectrum, inverse participation ratio, local probability amplitude, and more. Our proposal, combining achievable hopping dimerization and induced correlated disorder, presents a unique opportunity to study phenomenon of reentrant localization, generating significant research interest.

cond-mat.mes-hall↗

arXiv2023

Transport phenomena of TiCoSb: Defects induced modification in structure and density of states

TiCoSb1+x (x=0.0, 0.01, 0.02, 0.03, 0.04, 0.06) samples have been synthesized, employing solid state reaction method followed by arc menting. Theoretical calculations, using Density Functional Theory (DFT) have been performed to estimate band structure and density of states (DOS). Further, energitic calculations, using first principle have been carried out to reveal the formation energy for vacancy, interstitial, anti-site defects. Detail structural calculation, employing Rietveld refinement reveals the presence of embedded phases, vacancy and interstitial atom, which is also supported by the theoretical calculations. Lattice strain, crystalline size and dislocation density have been estimated by Williamson-Hall and modified Williamson-Hall methods. Thermal variation of resistivity [\r{ho}(T)] and thermopower [S(T)] have been explained using Mott equation and density of states (DOS) modification near the Fermi surface due to Co vancancy and embedded phases. Figure of merit (ZT) has been calculated and 4 to 5 times higher ZT for TiCoSb than earlier reported value is obtained at room temperature.

cond-mat.mtrl-sci↗

arXiv2023

Thermoelectric phenomena in an antiferromagnetic helix: Role of electric field

The charge and spin-dependent thermoelectric responses are investigated on a single-helical molecule possessing a collinear antiferromagnetic spin arrangement with zero net magnetization in the presence of a transverse electric field. Both the short and long-range hopping scenarios are considered, which mimic biological systems like single-stranded DNA and $α$-protein molecules. A non-equilibrium Green's function formalism is employed following the Landauer-Buttiker prescription to study the thermoelectric phenomena. The detailed dependence of the basic thermoelectric quantities on helicity, electric field, temperature etc., are elaborated on, and the underlying physics is explained accordingly. The charge and spin \textit{figure of merits} are computed and compared critically. For a more accurate estimation, the phononic contribution towards thermal conductance is also included. The present proposition shows a favorable spin-dependent thermoelectric response compared to the charge counterpart.

cond-mat.mes-hall↗

arXiv2023

Electrical analogue of one-dimensional and quasi-one-dimensional Aubry-André-Harper lattices

The present work discusses the possibility to realize correlated disorder in electrical circuits and studies the localization phenomena in terms of two-port impedance. The correlated disorder is incorporated using the Aubry-André-Harper (AAH) model. One-dimensional and quasi-one-dimensional AAH structures are explored and directly mapped with their tight-binding analogues. Transitions from the high-conducting phase to the low-conducting one are observed for the circuits.

cond-mat.dis-nn↗

arXiv2022

Antiferromagnetic helix as an efficient spin polarizer: Interplay between electric field and higher ordered hopping

We report spin filtration operation considering an antiferromagnetic helix system, possessing zero net magnetization. Common wisdom suggests that for such a system, a spin-polarized current is no longer available from a beam of unpolarized electrons. But, once we apply an electric field perpendicular to the helix axis, a large separation between up and down spin energy channels takes place which yields a high degree of spin polarization. Such a prescription has not been reported so far to the best of our concern. Employing a tight-binding framework to illustrate the antiferromagnetic helix, we compute spin filtration efficiency by determining spin selective currents using Landauer-Büttiker formalism. Geometrical conformation plays an important role in spin channel separation, and here we critically investigate the effects of short-range and long-range hoppings of electrons in presence of the electric field. We find that the filtration performance gets improved with increasing the range of hopping of electrons. Moreover, the phase of spin polarization can be altered selectively by changing the strength and direction of the electric field, and also by regulating the physical parameters that describe the antiferromagnetic helix. Finally, we explore the specific role of dephasing, to make the system more realistic and to make the present communication a self-contained one. Our analysis may provide a new route of getting conformation-dependent spin polarization possessing longer range hopping of electrons, and can be generalized further to different kinds of other fascinating antiferromagnetic systems.

cond-mat.mes-hall↗

arXiv2022

Transport characteristics of a $\mathcal{PT}$-symmetric non-Hermitian system: Effect of environmental interaction

The environmental influence is inevitable but often ignored in the study of electronic transport properties of small-scale systems. Such an environment-mediated interaction can generally be described by a parity-time symmetric non-Hermitian system with a balanced distribution of physical gain and loss. It is quite known in the literature that along with the conventional junction current, another current called bias-driven circular current can be established in a loop geometry depending upon the junction configuration. This current, further, induces a strong magnetic field that can even reach to few Tesla. What will happen to these quantities when the system interacts with its surrounding environment? Would it exhibit a detrimental response? We address such issues considering a two-terminal ring geometry where the junction setup is described within a tight-binding framework. All the transport quantities are evaluated using the standard Green's function formalism based on the Landauer-Büttiker approach.

cond-mat.mes-hall↗

arXiv2022

Strain-induced thermoelectricity in pentacene

The present work discusses a non-synthetic strategy to achieve a favorable thermoelectric response in pentacene via strain. It is found that a uni-axial strain is capable of inducing spatial anisotropy in the molecule. As a result, the transmission spectrum becomes highly asymmetric under a particular strained scenario, which is the primary requirement to get a favorable thermoelectric response. Different thermoelectric quantities are computed for the strain-induced pentacene using Green's function formalism following the Landauer-Buttiker prescription. Various scenarios are considered to make the present work more realistic, such as the effects of substrate, coupling strength between the molecule and electrodes, dangling bonds, etc. Such a scheme to enhance the thermoelectric performance in pentacene is technologically intriguing and completely new to the best of our knowledge.

cond-mat.mes-hall↗

arXiv2021

Enhanced current rectification in graphene nanoribbons: Effects of geometries and orientations of nanopores

We discuss the possibility of getting rectification operation in graphene nanoribbon (GNR). For a system to be a rectifier, it must be physically asymmetric and we induce the asymmetry in GNR by introducing nanopores. The rectification properties are discussed for differently structured nanopores. We find that shape and orientation of the nanopores are critical and sensitive to the degree of current rectification. As the choice of Fermi energy is crucial for obtaining significant current rectification, explicit dependence of Fermi energy on the degree of current rectification is also studied for a particular shape of the nanopore. Finally, the role of nanopore size and different spatial distributions of the electrostatic potential profile across the GNR are discussed. Given the simplicity of the proposed method and promising results, the present proposition may lead to a new route of getting current rectification in different kinds of materials where nanopores can be formed selectively.

cond-mat.mes-hall↗

arXiv2021

Magnetic response of interacting electrons in a spatially non-uniform disordered multi-channel system: Exact and mean-field results

In this work we explore magnetic response of interacting electrons in a spatially non-uniform disordered system, where impurities are introduced in one sector of the geometry keeping the other one free. The interaction among the electrons are taken in the well known Hubbard form which leads to several anomalous features in energy spectra and flux driven circular current, depending on the concentration of up and down spin electrons. For smaller systems with less number of electrons we present exact results which always give a clear picture to understand the basic mechanisms, while for large systems having higher number of electrons mean-field results are given. The effect of disorder is very interesting. Beyond a critical disorder, completely contrasting signature is obtained compared to uniform disordered systems, and the phenomenon becomes more promising when the Hubbard interaction is included. Along with these features, we find unusual half flux-quantum periodic current at some typical cases and a suitable explanation of it is provided. Our detailed analysis may be utilized to study magnetic response of interacting electrons in other similar kind of non-uniform disordered systems.

cond-mat.mes-hall↗

arXiv2021

Localization to delocalization transition in a double stranded helical geometry: Effects of conformation, transverse electric field and dynamics

Conformational effect on electronic localization is critically investigated for the first time considering a double-stranded helical geometry (DSHG) subjected to an electric field. In the presence of electric field the DSHG behaves like a correlated disordered system whose site potentials are modulated in a cosine form like the well known Aubry-Andre-Harper (AAH) model. The potential distribution can be modulated further by changing the orientation of the incident field. A similar kind of cosine modulation is also introduced in the inter-strand hopping integrals of the DSHG. Suitably adjusting the orientation of the electric field, we can achieve fully extended energy eigenstates or completely localized ones or a mixture of both. The effects of short-range and long-range hopping integrals along with the chirality on localization are thoroughly studied. Finally, we inspect the role of helical dynamics to make the model more realistic. The interplay between the helical geometry and electric field may open up several notable features of electronic localization and can be verified by using different chiral molecules.

cond-mat.mes-hall↗

arXiv2021

A driven fractal network: Possible route to efficient thermoelectric application

An essential attribute of many fractal structures is self-similarity. A Sierpinski gasket (SPG) triangle is a promising example of a fractal lattice that exhibits localized energy eigenstates. In the present work, for the first time we establish that a mixture of both extended and localized energy eigenstates can be generated yeilding mobility edges at multiple energies in presence of a time-periodic driving field. We obtain several compelling features by studying the transmission and energy eigenvalue spectra. As a possible application of our new findings, different thermoelectric properties are discussed, such as electrical conductance, thermopower, thermal conductance due to electrons and phonons. We show that our proposed method indeed exhibits highly favorable thermoelectric performance. The time-periodic driving field is assumed through an arbitrarily polarized light, and its effect is incorporated via Floquet-Bloch ansatz. All transport phenomena are worked out using Green's function formalism following the Landauer-Büttiker prescription.

cond-mat.mes-hall↗

arXiv2021

Spin-dependent transport in a driven noncolinear antiferromagnetic fractal network

Noncolinear magnetic texture breaks the spin-sublattice symmetry which gives rise to a spin-splitting effect. Inspired by this, we study the spin-dependent transport properties in a noncolinear antiferromagnetic fractal structure, namely, the Sierpinski Gasket (SPG) triangle. We find that though the spin-up and spin-down currents are different, the degree of spin polarization is too weak. Finally, we come up with a proposal, where the degree of spin polarization can be enhanced significantly in the presence of a time-periodic driving field. Such a prescription of getting spin-filtering effect from an unpolarized source in a fractal network is completely new to the best of our knowledge. Starting from a higher generation of SPG to smaller ones, the precise dependencies of driving field parameters, spin-dependent scattering strength, interface sensitivity on spin polarization are critically investigated. The spatial distribution of spin-resolved bond current density is also explored. Interestingly, our proposed setup exhibits finite spin polarization for different spin-quantization axes. Arbitrarily polarized light is considered and its effect is incorporated through Floquet-Bloch ansatz. All the spin-resolved transport quantities are computed using Green's function formalism following the Landauer-Büttiker prescription. The present work brings forth new insights into spintronic properties of noncolinear antiferromagnetic SPG and should entice the AFM spintronic community to explore other fractal structures with the possibility of unconventional features.

cond-mat.mes-hall↗

arXiv2019

Anomalous transport through algebraically localized states in one-dimension

Localization in one-dimensional disordered or quasiperiodic non-interacting systems in presence of power-law hopping is very different from localization in short-ranged systems. Power-law hopping leads to algebraic localization as opposed to exponential localization in short-ranged systems. Exponential localization is synonymous with insulating behavior in the thermodynamic limit. Here we show that the same is not true for algebraic localization. We show, on general grounds, that depending on the strength of the algebraic decay, the algebraically localized states can be actually either conducting or insulating in thermodynamic limit. We exemplify this statement with explicit calculations on the Aubry-André-Harper model in presence of power-law hopping, with the power-law exponent $α>1$, so that the thermodynamic limit is well-defined. We find a phase of this system where there is a mobility edge separating completely delocalized and algebraically localized states, with the algebraically localized states showing signatures of super-diffusive transport. Thus, in this phase, the mobility edge separates two kinds of conducting states, ballistic and super-diffusive. We trace the occurrence of this behavior to near-resonance conditions of the on-site energies that occur due to the quasi-periodic nature of the potential.

cond-mat.dis-nn↗

arXiv2019

Spin-selective transmission through a single-stranded magnetic helix

Magnetic helix (MH) structure can be a role model for future spintronic devices. Utilizing the advantage of constructing possible magnetic configurations, in the present work first time we investigate spintronic behavior, to the best of our knowledge, in a helical geometry with finite magnetic ordering. The interplay between short-range and long-range hopping of electrons yields many non-trivial features which are thoroughly studied. Quite interestingly we see that the MH exhibits the strong chiral-induced spin selectivity effect, like what is observed in chiral molecules. Finally, to make the model more realistic we also examine the effect of helical dynamics. All the results are valid for a wide range of physical parameters, which prove the robustness of our analysis.

cond-mat.mes-hall↗

arXiv2019

More current with less particles due to power-law hopping

We reveal interesting universal transport behavior of ordered one-dimensional fermionic systems with power-law hopping. We restrict ourselves to the case where the power-law decay exponent $α>1$, so that the thermodynamic limit is well-defined. We explore the quantum phase-diagram of the non-interacting model in terms of the zero temperature Drude weight, which can be analytically calculated. Most interestingly, we reveal that for $1<α<2$, there is a phase where the zero temperature Drude weight diverges as filling fraction goes to zero. Thus, in this regime, counter intuitively, reducing number of particles increases transport and is maximum for a sub-extensive number of particles. Being a statement about zero-filling, this transport behavior is immune to adding number conserving interaction terms. We have explicitly checked this using two different interacting systems. We propose that measurement of persistent current due to a flux through a mesoscopic ring with power-law hopping will give an experimental signature of this phase. In persistent current, the signature of this phase survives up to a finite temperature for a finite system. At higher temperatures, a crossover is seen. The maximum persistent current shows a power-law decay at high temperatures. This is in contrast with short ranged systems, where the persistent current decays exponentially with temperature.

cond-mat.mes-hall↗

arXiv2019

Bias induced circular spin current: Effects of environmental dephasing and disorder

Analogous to circular spin current in an isolated quantum loop, bias induced spin circular current can also be generated under certain physical conditions in a nanojunction having single and/or multiple loop geometries which we propose first time, to the best of our concern, considering a magnetic quantum system. The key aspect of our work is the development of a suitable theory for defining and analyzing circular spin current in presence of environmental dephasing and impurities. Unlike transport current in a conducting junction, circular current may enhance significantly in presence of disorder and phase randomizing processes. Our analysis provides a new spin dependent phenomenon, and can give important signatures in designing suitable spintronic devices as well as selective spin regulations.

cond-mat.mes-hall↗