In this work we report for the first time, to the best of our knowledge, the tunable electronic p... more In this work we report for the first time, to the best of our knowledge, the tunable electronic properties of beta-borophene (BB) on the polar substrate ( Zr O 2 ). We provide an analytical prescription for the calculation of ground state energy in the presence of the electron–phonon (e-ph) interaction, within the framework of the Lee-Low-Pines theory. In the theoretical investigation of the polaron formation in BB, we describe its effective masses, polaronic band-gap, mobility, and Fermi velocities, which are different in each coordinate due to the out-of-plane buckling structure. We also analyze how the average effective mass and Fermi velocities of the charge carriers in the buckling structure are affected by the external magnetic field. It is shown that the polaronic energy becomes more effective in presence of a magnetic field, which we confirm through an analytical prescription. The characteristics of the evolution of average effective mass and average effective Fermi velocity...
Journal of Computational and Theoretical Nanoscience, 2009
We explore electron transport properties in a quantum wire attached to two metallic electrodes. A... more We explore electron transport properties in a quantum wire attached to two metallic electrodes. A simple tight-binding model is used to describe the system and the coupling of the wire to the electrodes (source and drain) is treated through Newns-Anderson chemisorption theory. In our present model, the site energies of the wire are characterized by the relation ǫ i = W cos (iλ ν π) where W , λ, ν are three positive numbers. For ν = 0, the threshold bias voltage of electron conduction across the bridge can be controlled very nicely by tuning the strength of the potential W. On the other hand, for ν = 0, the wire becomes an aperiodic one and quite interestingly we see that, for some special values of ν, the system exhibits a metal-insulator transition which provides a significant feature in this particular study. Our numerical results may be useful for fabrication of efficient switching devices.
TiCoSb1+x (x=0.0, 0.01, 0.02, 0.03, 0.04, 0.06) samples have been synthesized, employing solid st... more 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 [ρ(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.
We investigate magnetic response in mesoscopic rings and moebius strips penetrated by magnetic fl... more We investigate magnetic response in mesoscopic rings and moebius strips penetrated by magnetic flux φ. Based on a simple tight-binding framework all the calculations are performed numerically which describe persistent current and low-field magnetic susceptibility as functions of magnetic flux φ, total number of electrons N e , system size N and disorder strength W. Our exact analysis may provide some important signatures to study magnetic response in nano-scale loop geometries.
A new way of getting controlled spin dependent transport through a two-terminal bridge setup is e... more A new way of getting controlled spin dependent transport through a two-terminal bridge setup is explored. The system comprises a magnetic quantum ring which is directly coupled to a magnetic quantum wire and subjected to an in-plane electric field perpendicular to the wire. Without directly changing system parameters, one can regulate spin currents simply by tuning the external electric field under a finite bias drop across the wire. For some particular field strengths a high degree of spin polarization can be achieved and thus the system can essentially be utilized as an externally controlled spin polarized device. A detailed comparison of spin current magnitudes obtained from other bridge setups is also examined to make the present investigation a self contained study.
To acknowledge and cite the published work "Interface sensitivity in quantum transport through si... more To acknowledge and cite the published work "Interface sensitivity in quantum transport through single molecules" of K. Tagami, L. Wang and M. Tsukada. The reference of this work is: Nano Lett. 4, 209 (2004). To acknowledge and cite the published work "The role of quantum interference in determining transport properties of molecular bridges" of K. Walczak. The reference of this work is: Central Eur. J. Chem. 2, 524 (2004).
Journal of Physics: Condensed Matter, Oct 11, 2022
Efficient thermoelectric (TE) energy conversion is one of the most desirable solutions of our cur... more Efficient thermoelectric (TE) energy conversion is one of the most desirable solutions of our current day energy crisis. Exploiting the effect of quantum interference among electronic waves, in this work we propose a prescription of getting high TE efficiency, the so-called figure of merit (ZT), considering an interferometric geometry where a loop conductor is clamped between two heat baths. Unlike conventional junction configurations, we introduce an additional path for electron transfer directly from source to drain, due to their close proximity. The interplay between different paths leads to an enhanced ZT (ZT > 1). Moreover, the efficiency can be further regulated by tuning the inter-electrode coupling. The effects of magnetic flux threaded by the ring and disorder are also discussed. Our proposed prescription may lead to a new route of designing tunable TE devices at nanoscale level.
A novel feature of electron transport is explored through a thin film of varying impurity density... more 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.
We study electron transport properties of some molecular wires and a unconventional disordered th... more 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.
Journal of Physics: Condensed Matter, Sep 24, 2020
Antiferromagnetic materials can be the suitable functional elements for designing of future spin ... more Antiferromagnetic materials can be the suitable functional elements for designing of future spin based electronic devices, circumventing the use of conventional ferromagnetic materials and spin–orbit coupled systems. In the present work first time we put forward the underlying physical mechanism, to the best of our knowledge, to generate polarized spin current through a magnetic material having zero net magnetization. Our proposal is substantiated by considering a 2D geometry which is composed of several concentric 1D rings where neighboring rings are mutually connected with each other. The misalignment of up and down spin bands, which is the primary requirement to have finite spin polarization, is described analytically and then several aspects of spin polarization are studied numerically. Finally, we discuss experimental realization of the proposed magnetic quantum system. Our analysis can be utilized to any other complicated magnetic geometries, and may open up a new platform for future spintronic applications.
We make an in-depth analysis of electronic transport and localization properties of non-interacti... more We make an in-depth analysis of electronic transport and localization properties of non-interacting electrons in a Sierpinski gasket (SPG) fractal lattice in presence of magnetic field within a tight-binding framework. Unlike conventional symmetric systems, asymmetric SPG triangle leads to more conducting behavior, and thus delocalization of energy states, which we examine by calculating magnetic flux driven circular current and inverse participation ratio. The spectral peculiarity, that is the gapped nature of energy spectrum in fractal lattices, is clearly reflected from the variation of current with electron filling, yielding possibilities of getting filling dependent switching action. The effect of temperature is also discussed. Our analysis can be utilized to study magnetotransport properties in any other fractal lattices having loop sub-structures.
Journal of Computational and Theoretical Nanoscience, Mar 1, 2010
We explore NOT gate response in a mesoscopic ring threaded by a magnetic flux φ. The ring is atta... more We explore NOT gate response in a mesoscopic ring threaded by a magnetic flux φ. The ring is attached symmetrically to two semi-infinite one-dimensional metallic electrodes and a gate voltage, viz, V a , is applied in one arm of the ring which is treated as the input of the NOT gate. 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 ring-to-electrodes coupling strength, magnetic flux and gate voltage. Our theoretical study shows that, for φ = φ 0 /2 (φ 0 = ch/e, the elementary flux-quantum) a high output current (1) (in the logical sense) appears if the input to the gate is low (0), while a low output current (0) appears when the input to the gate is high (1). It clearly exhibits the NOT gate behavior and this aspect may be utilized in designing an electronic logic gate.
The microwave rotational spectra of ortho-tolunitrile (C6H4CH3CN) have been investigated in the g... more The microwave rotational spectra of ortho-tolunitrile (C6H4CH3CN) have been investigated in the ground torsional state in the frequency ranges of 22.0-26.0 GHz and 32.0-37.0 GHz. The true rotational constants were determined to be Ar = 2890.98 MHz, Br = 1499.75 MHz, and Cr = 993.58 MHz. A least-squares analysis of the A - E splittings of 16 transitions resulted in the values of V3 = 533.53 cal/mol and thetaa = 54.22 degrees, assuming V6 = 0 and Ialpha = 3.2 a.m.u. Å2. Copyright 1998 Academic Press.
We explore electron transport through a moebius strip attached to two metallic electrodes by the ... more 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.
Journal of the Physical Society of Japan, Nov 15, 2009
We describe XNOR gate response in a mesoscopic ring threaded by a magnetic flux φ. The ring is at... more We describe XNOR gate response in a mesoscopic ring threaded by a magnetic flux φ. The ring is attached symmetrically to two semi-infinite one-dimensional metallic electrodes and two gate voltages, viz, V a and V b , are applied in one arm of the ring which are treated as the inputs of the XNOR gate. 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 ring-to-electrode coupling strength, magnetic flux and gate voltages. Our theoretical study shows that, for a particular value of φ (= φ 0 /2) (φ 0 = ch/e, the elementary flux-quantum), a high output current (1) (in the logical sense) appears if both the two inputs to the gate are the same, while if one but not both inputs are high (1), a low output current (0) results. It clearly exhibits the XNOR gate behavior and this aspect may be utilized in designing an electronic logic gate.
We address XOR gate response in a mesoscopic ring threaded by a magnetic flux φ. The ring, compos... more We address XOR gate response in a mesoscopic ring threaded by a magnetic flux φ. The ring, composed of identical quantum dots, is symmetrically attached to two semi-infinite one-dimensional metallic electrodes and two gate voltages, viz, V a and V b , are applied, respectively, in each arm of the ring which are treated as the two inputs of the XOR gate. 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 ring-electrodes coupling strengths, magnetic flux and gate voltages. Quite interestingly it is observed that, for φ = φ 0 /2 (φ 0 = ch/e, the elementary flux-quantum) a high output current (1) (in the logical sense) appears if one, and only one, of the inputs to the gate is high (1), while if both inputs are low (0) or both are high (1), a low output current (0) appears. It clearly demonstrates the XOR behavior and this aspect may be utilized in designing the electronic logic gate.
In this work we report for the first time, to the best of our knowledge, the tunable electronic p... more In this work we report for the first time, to the best of our knowledge, the tunable electronic properties of beta-borophene (BB) on the polar substrate ( Zr O 2 ). We provide an analytical prescription for the calculation of ground state energy in the presence of the electron–phonon (e-ph) interaction, within the framework of the Lee-Low-Pines theory. In the theoretical investigation of the polaron formation in BB, we describe its effective masses, polaronic band-gap, mobility, and Fermi velocities, which are different in each coordinate due to the out-of-plane buckling structure. We also analyze how the average effective mass and Fermi velocities of the charge carriers in the buckling structure are affected by the external magnetic field. It is shown that the polaronic energy becomes more effective in presence of a magnetic field, which we confirm through an analytical prescription. The characteristics of the evolution of average effective mass and average effective Fermi velocity...
Journal of Computational and Theoretical Nanoscience, 2009
We explore electron transport properties in a quantum wire attached to two metallic electrodes. A... more We explore electron transport properties in a quantum wire attached to two metallic electrodes. A simple tight-binding model is used to describe the system and the coupling of the wire to the electrodes (source and drain) is treated through Newns-Anderson chemisorption theory. In our present model, the site energies of the wire are characterized by the relation ǫ i = W cos (iλ ν π) where W , λ, ν are three positive numbers. For ν = 0, the threshold bias voltage of electron conduction across the bridge can be controlled very nicely by tuning the strength of the potential W. On the other hand, for ν = 0, the wire becomes an aperiodic one and quite interestingly we see that, for some special values of ν, the system exhibits a metal-insulator transition which provides a significant feature in this particular study. Our numerical results may be useful for fabrication of efficient switching devices.
TiCoSb1+x (x=0.0, 0.01, 0.02, 0.03, 0.04, 0.06) samples have been synthesized, employing solid st... more 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 [ρ(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.
We investigate magnetic response in mesoscopic rings and moebius strips penetrated by magnetic fl... more We investigate magnetic response in mesoscopic rings and moebius strips penetrated by magnetic flux φ. Based on a simple tight-binding framework all the calculations are performed numerically which describe persistent current and low-field magnetic susceptibility as functions of magnetic flux φ, total number of electrons N e , system size N and disorder strength W. Our exact analysis may provide some important signatures to study magnetic response in nano-scale loop geometries.
A new way of getting controlled spin dependent transport through a two-terminal bridge setup is e... more A new way of getting controlled spin dependent transport through a two-terminal bridge setup is explored. The system comprises a magnetic quantum ring which is directly coupled to a magnetic quantum wire and subjected to an in-plane electric field perpendicular to the wire. Without directly changing system parameters, one can regulate spin currents simply by tuning the external electric field under a finite bias drop across the wire. For some particular field strengths a high degree of spin polarization can be achieved and thus the system can essentially be utilized as an externally controlled spin polarized device. A detailed comparison of spin current magnitudes obtained from other bridge setups is also examined to make the present investigation a self contained study.
To acknowledge and cite the published work "Interface sensitivity in quantum transport through si... more To acknowledge and cite the published work "Interface sensitivity in quantum transport through single molecules" of K. Tagami, L. Wang and M. Tsukada. The reference of this work is: Nano Lett. 4, 209 (2004). To acknowledge and cite the published work "The role of quantum interference in determining transport properties of molecular bridges" of K. Walczak. The reference of this work is: Central Eur. J. Chem. 2, 524 (2004).
Journal of Physics: Condensed Matter, Oct 11, 2022
Efficient thermoelectric (TE) energy conversion is one of the most desirable solutions of our cur... more Efficient thermoelectric (TE) energy conversion is one of the most desirable solutions of our current day energy crisis. Exploiting the effect of quantum interference among electronic waves, in this work we propose a prescription of getting high TE efficiency, the so-called figure of merit (ZT), considering an interferometric geometry where a loop conductor is clamped between two heat baths. Unlike conventional junction configurations, we introduce an additional path for electron transfer directly from source to drain, due to their close proximity. The interplay between different paths leads to an enhanced ZT (ZT > 1). Moreover, the efficiency can be further regulated by tuning the inter-electrode coupling. The effects of magnetic flux threaded by the ring and disorder are also discussed. Our proposed prescription may lead to a new route of designing tunable TE devices at nanoscale level.
A novel feature of electron transport is explored through a thin film of varying impurity density... more 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.
We study electron transport properties of some molecular wires and a unconventional disordered th... more 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.
Journal of Physics: Condensed Matter, Sep 24, 2020
Antiferromagnetic materials can be the suitable functional elements for designing of future spin ... more Antiferromagnetic materials can be the suitable functional elements for designing of future spin based electronic devices, circumventing the use of conventional ferromagnetic materials and spin–orbit coupled systems. In the present work first time we put forward the underlying physical mechanism, to the best of our knowledge, to generate polarized spin current through a magnetic material having zero net magnetization. Our proposal is substantiated by considering a 2D geometry which is composed of several concentric 1D rings where neighboring rings are mutually connected with each other. The misalignment of up and down spin bands, which is the primary requirement to have finite spin polarization, is described analytically and then several aspects of spin polarization are studied numerically. Finally, we discuss experimental realization of the proposed magnetic quantum system. Our analysis can be utilized to any other complicated magnetic geometries, and may open up a new platform for future spintronic applications.
We make an in-depth analysis of electronic transport and localization properties of non-interacti... more We make an in-depth analysis of electronic transport and localization properties of non-interacting electrons in a Sierpinski gasket (SPG) fractal lattice in presence of magnetic field within a tight-binding framework. Unlike conventional symmetric systems, asymmetric SPG triangle leads to more conducting behavior, and thus delocalization of energy states, which we examine by calculating magnetic flux driven circular current and inverse participation ratio. The spectral peculiarity, that is the gapped nature of energy spectrum in fractal lattices, is clearly reflected from the variation of current with electron filling, yielding possibilities of getting filling dependent switching action. The effect of temperature is also discussed. Our analysis can be utilized to study magnetotransport properties in any other fractal lattices having loop sub-structures.
Journal of Computational and Theoretical Nanoscience, Mar 1, 2010
We explore NOT gate response in a mesoscopic ring threaded by a magnetic flux φ. The ring is atta... more We explore NOT gate response in a mesoscopic ring threaded by a magnetic flux φ. The ring is attached symmetrically to two semi-infinite one-dimensional metallic electrodes and a gate voltage, viz, V a , is applied in one arm of the ring which is treated as the input of the NOT gate. 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 ring-to-electrodes coupling strength, magnetic flux and gate voltage. Our theoretical study shows that, for φ = φ 0 /2 (φ 0 = ch/e, the elementary flux-quantum) a high output current (1) (in the logical sense) appears if the input to the gate is low (0), while a low output current (0) appears when the input to the gate is high (1). It clearly exhibits the NOT gate behavior and this aspect may be utilized in designing an electronic logic gate.
The microwave rotational spectra of ortho-tolunitrile (C6H4CH3CN) have been investigated in the g... more The microwave rotational spectra of ortho-tolunitrile (C6H4CH3CN) have been investigated in the ground torsional state in the frequency ranges of 22.0-26.0 GHz and 32.0-37.0 GHz. The true rotational constants were determined to be Ar = 2890.98 MHz, Br = 1499.75 MHz, and Cr = 993.58 MHz. A least-squares analysis of the A - E splittings of 16 transitions resulted in the values of V3 = 533.53 cal/mol and thetaa = 54.22 degrees, assuming V6 = 0 and Ialpha = 3.2 a.m.u. Å2. Copyright 1998 Academic Press.
We explore electron transport through a moebius strip attached to two metallic electrodes by the ... more 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.
Journal of the Physical Society of Japan, Nov 15, 2009
We describe XNOR gate response in a mesoscopic ring threaded by a magnetic flux φ. The ring is at... more We describe XNOR gate response in a mesoscopic ring threaded by a magnetic flux φ. The ring is attached symmetrically to two semi-infinite one-dimensional metallic electrodes and two gate voltages, viz, V a and V b , are applied in one arm of the ring which are treated as the inputs of the XNOR gate. 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 ring-to-electrode coupling strength, magnetic flux and gate voltages. Our theoretical study shows that, for a particular value of φ (= φ 0 /2) (φ 0 = ch/e, the elementary flux-quantum), a high output current (1) (in the logical sense) appears if both the two inputs to the gate are the same, while if one but not both inputs are high (1), a low output current (0) results. It clearly exhibits the XNOR gate behavior and this aspect may be utilized in designing an electronic logic gate.
We address XOR gate response in a mesoscopic ring threaded by a magnetic flux φ. The ring, compos... more We address XOR gate response in a mesoscopic ring threaded by a magnetic flux φ. The ring, composed of identical quantum dots, is symmetrically attached to two semi-infinite one-dimensional metallic electrodes and two gate voltages, viz, V a and V b , are applied, respectively, in each arm of the ring which are treated as the two inputs of the XOR gate. 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 ring-electrodes coupling strengths, magnetic flux and gate voltages. Quite interestingly it is observed that, for φ = φ 0 /2 (φ 0 = ch/e, the elementary flux-quantum) a high output current (1) (in the logical sense) appears if one, and only one, of the inputs to the gate is high (1), while if both inputs are low (0) or both are high (1), a low output current (0) appears. It clearly demonstrates the XOR behavior and this aspect may be utilized in designing the electronic logic gate.
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Papers by Santanu Maiti