Milan Damnjanovic | University of Belgrade (original) (raw)

Papers by Milan Damnjanovic

arXiv (Cornell University), Aug 26, 2021

All of 320 layer groups, distributed into 80 clusters-single/double ordinary/gray groups-are used... more All of 320 layer groups, distributed into 80 clusters-single/double ordinary/gray groups-are used to complete systematization of linear (in all directions) band crossings and corresponding effective Hamiltonians in high-symmetry Brillouin zone points of layered materials, refining and expanding in literature existing data. Two-and four-dimensional effective Hamiltonians are determined by the allowed (half)integer (co)representations of the same dimension in the crossing point and one-or two-dimensional generic allowed representations. The resulting dispersion types (having isotropic or anisotropic form) are: single cone (with double degenerate crossing point and nondegenerate branches, or 4-fold degenerate crossing point with double degenerate conical branches), poppy-flower (4-fold degenerate crossing point with two pairs of non-degenerate mutually rotated conical branches), and a fortune teller (with nodal lines). Transition to double group, enabling to include spin-orbit interaction, results in various scenarios at high symmetry points: gap closing, gap opening, cone preserving, cone splitting etc. Analogously, analyzing ordinary to gray group transitions, the role of time reversal symmetry is clarified. I. INTRODUCTION Interplay between symmetry and topology of band structures is among the most attractive topics in contemporary condensed matter physics. Besides topological insulators (TIs), nodal semimetals take a notable role, being a material realization of relativistic Dirac, Weyl, and Majorana particles [1-3], or lead to the emergence of unconventional quasiparticles [4-7]. Characterized by band crossings (touching) points (lines) at Fermi level, with energies dispersing linearly, they have various interesting properties: Dirac points represent the interphases between topologically different insulating phases, Weyl points lead to semimetals with chiral anomaly, Fermi arc surface states etc. Protected by crystal symmetries [8-15], these crossing points are robust with respect to various symmetry-preserving perturbations. Energy of the crossing cannot be predicted by symmetry alone; particularly important are those on Fermi level: when placed at (special) high symmetry points (HSPs) in Brillouin zone (BZ), the material is known as a symmetry-enforced semimetal.

Acta Physica Polonica A, Aug 1, 2011

More than fifteen years have passed since the first report of experimental evidence of regularly ... more More than fifteen years have passed since the first report of experimental evidence of regularly coiled carbon nanotubes, but, the structure, formation mechanism and theoretical aspects of these nanotubes still remain unresolved. We propose model of hexagonal, helically coiled single wall carbon nanotubes, determine their line group symmetry and calculate electronic band structure of the relaxed configurations by means of fully symmetry adopted density functional tight binding method implemented into the POLSym code. Electrical properties of the straight and coiled carbon nanotubes of different chiralities are compared and analyzed.

Physica Status Solidi B-basic Solid State Physics, Sep 5, 2014

Thermal conductivity is one of the most interesting physical properties of carbon nanotubes. This... more Thermal conductivity is one of the most interesting physical properties of carbon nanotubes. This quantity has been extensively explored experimentally and theoretically using different approaches like: molecular dynamics simulation, Boltzmann-Peierls phonon transport equation, modified wave-vector model etc. Results of these investigations are of great interest and show that carbon-based materials, graphene and nanotubes in particular, show high values of thermal conductivity. Thus, carbon nanotubes are a good candidate for the future applications as thermal interface materials. In this paper we present the results of thermal conductance  of a model of helically coiled carbon nanotubes (HCCNTs), obtained from phonon dispersion relations. Calculation of  of HCCNTs is based on the Landauer theory where phonon relaxation rate is obtained by simple Klemens-like model.

arXiv (Cornell University), Jun 28, 2023

Vanishing of the total angular momentum of the electrons occupying all orbitals of a closed shell... more Vanishing of the total angular momentum of the electrons occupying all orbitals of a closed shell in an atom is a textbook fact. Understanding the symmetry content of the atomic shell as irreducible representation of angular momentum, enables straightforward transfer of the notion to (translational or helically) periodic systems. More relevant generalizations naturally appear: stratum shell is intermediate step to physically sound band representations, including elementary and basic ones and connected components. We show that nontrivial determinant representation indicates stable topology of band in single colorless layer groups and obstructive limit in in single colorless line groups.

Meeting abstracts, 2012

not Available.

Journal of Physics A: Mathematical and Theoretical

Full sets of inequivalent elementary band co-representations (coEBRs) for spinless and spinful sy... more Full sets of inequivalent elementary band co-representations (coEBRs) for spinless and spinful systems with grey line group (LG) symmetry are calculated and, together with recently reported elementary band representation (EBRs) for colorless single and double LGs by Milošević et al (2020 J. Phys. A: Math. Theor. 53 455204), the task of characterization of nonmagnetic quasi-one-dimensional (quasi-1D) topological crystals by means of the theory of topological quantum chemistry can be completed. Effects of additional time reversal symmetry on band topology and applicability of topological quantum chemistry is thoroughly analyzed. The main conclusions of the latter are illustrated on spinful Su–Schrieffer–Heeger model (topological mirror chain). Technique of induction and decomposition of coEBRs is fully developed and presented in detail. Complete sets of coEBRs for all thirteen families of single and double grey LGs are tabulated. Quasi-1D structures with symmetry enforced hourglass fe...

physica status solidi (b)

Spin-orbit induced phenomena in quasi-one-dimensional systems are analyzed with the help of doubl... more Spin-orbit induced phenomena in quasi-one-dimensional systems are analyzed with the help of double line groups and their irreducible representations. Orbital band splitting and removal of the spin degeneracy are found to be incompatible with vertical mirror symmetry, as well as with simultaneous invariance under the time reversal and horizontal (roto) reflections. This singles out systems with the first and the fifth family line group symmetry as the only candidates for spin polarized currents; direction of electron spin polarization is also determined by the system symmetry. When applied to carbon nanotubes the developed theory enlightens a number of interesting results concerning the band topology and spin polarization of bands.

Acta Crystallographica Section A Foundations and Advances, 2022

Considered are 80 sets of layer groups, each set consisting of four groups: ordinary single and d... more Considered are 80 sets of layer groups, each set consisting of four groups: ordinary single and double, and grey single and double layer groups. The structural properties of layer groups (factorization into cyclic subgroups and the existence of grading according to the sequence of halving subgroups) enable efficient symbolic computation (by the POLSym code) of the relevant properties, real and complex irreducible and allowed (half-)integer (co-)representations in particular. This task includes, as the first step, classification of the irreducible domains based on the group action in the Brillouin zone combined with torus topology. Also, the band (co-)representations induced from the irreducible (co-)representations of Wyckoff-position stabilizers (site-symmetry groups) are decomposed into the irreducible components. These, and other layer group symmetry related theoretical data relevant for physics, layered materials in particular, are tabulated and made available through the web si...

Contemporary Materials, 2016

We studied electron transport in single wall carbon nanotubes placed in stationary homogeneous el... more We studied electron transport in single wall carbon nanotubes placed in stationary homogeneous electric fields, oriented along tubes. Electron distributions for various electric fields are determined by solving stationary multi bands Boltzmann transport equation in presence of electron phonon scattering mechanisms. Contributions of all possible scattering channels, allowed by selection rules and energy conservation, are taken into account for finding scattering rate and collision integrals. As it is previously predicted, large electron drift velocities in straight single wall carbon nanotubes are obtained. Frequent electron scattering as well as low group velocity have strong impact on reduction of drift velocity in helically coiled carbon nanotubes.

Contemporary Materials, 2015

Semiconducting single wall carbon nanotubes (SWCNTs) exhibit high electron mobility in low electr... more Semiconducting single wall carbon nanotubes (SWCNTs) exhibit high electron mobility in low electric field. Tube diameter and temperature have been found to strongly affect transport properties of SWCNTs. We have investigated electron mobility of helically coiled carbon nanotubes (HCCNTs). Electron and phonon band structures of HCCNTs are used in calculation of electron-phonon matrix elements. Scattering rates are calculated using the first order perturbation theory while taking care of energy and momentum conservation law. In order to obtain electron drift velocities, steady state simulation of charge transport is performed using Monte Carlo method.

We show that modified Wigner projector technique and generalized Bloch theorem approach yield max... more We show that modified Wigner projector technique and generalized Bloch theorem approach yield maximally efficient diagonalization of the Hamiltonian of the large symmetrical systems. For the sake of illustration, we perform a case study of the simplified DNA molecule model and solve the energy eigenproblem analytically by using the unit symmetry cell (symcell) and the corresponding low-dimensional subspaces only. Relevant dynamical parameters are automatically obtained, enabling direct interpretation of the result. Effectiveness of the procedure is based on the two key points: (1) replacing infinite sums over the group elements by modified group projectors which are inherently determined by the group generators only; (2) reducing the dynamics of the system (from the infinite dimensional state space) to the low-dimensional symcell subspace, taking the benefit from the induced structure of the state space. Unlike the original Wigner projectors, the modified group projector technique i...

Contemporary Materials, 2016

We studied the stationary electron transport of semiconduction single-wall straight and helically... more We studied the stationary electron transport of semiconduction single-wall straight and helically coiled carbon nanotubes in the presence of electron- phonon interaction. The electron and phonon bands as well as electron phonon coupling matrix elements are obtained from quantum mechanical calculations with the application of symmetry. Total scattering rate for all electronic states relevant for charge transport is obtained as a sum over independent processes. Transport simulation is realized by Monte Carlo algorithm, where free flight time and scattering mechanism are selected randomly. The obtained electron transport properties of helically coiled and straight carbon nanotubes are significantly different. The electron drift velocities in helically coiled nanotubes are several times lower than in straight carbon nanotubes.

Contemporary Materials, 2017

Experimentally is confirmed that helically coiled carbon nanotube (HCCNT) could be used as a smal... more Experimentally is confirmed that helically coiled carbon nanotube (HCCNT) could be used as a small solenoid for generating spatially localized magnetic field. Current distribution during diffusive electronic transport likewise the inductivity of this quantum conductor depends on electric field. Despite slightly lower electron mobility in HCCNTs than that of the straight single wall carbon nanotubes, the coiled nanotubes are attractive for application as nonlinear nano-solenoids. Nonequilibrium electron distribution functions obtained by solving Boltzmann transport equation are used to predict average helical radius of current flow as a function of electric field intensity. Change of spatial distribution of electronic flow with applied electric field is considered and nonlinear inductivity of HCCNT is predicted.

Contemporary Materials, 2014

Thermal conductivity is one of the most interesting physical properties of carbon nanotubes. This... more Thermal conductivity is one of the most interesting physical properties of carbon nanotubes. This quantity has been extensively explored experimentally and theoretically using different approaches like: molecular dynamics simulation, Boltzmann-Peierls phonon transport equation, modified wave-vector model etc. Results of these investigations are of great interest and show that carbon- based materials, graphene and nanotubes in particular, show high values of thermal conductivity. Thus, carbon nanotubes are a good candidate for the future applications as thermal interface materials. In this paper we present the results of thermal conductance s of a model of helically coiled carbon nanotubes (HCCNTs), obtained from phonon dispersion relations. Calculation of s of HCCNTs is based on the Landauer theory where phonon relaxation rate is obtained by simple Klemens-like model.

Journal of Physics A: Mathematical and Theoretical, 2020

Quantized topological invariants characterizing topological phases in quasi-1D materials are usua... more Quantized topological invariants characterizing topological phases in quasi-1D materials are usually considered only on the basis of spatial inversion parity eigenvalues. However, symmetry of quasi-1D systems is far more complex and their complete topological characterisation can be obtained only on the basis of elementary band representations (EBRs) for the relevant symmetry groups. We derive complete sets of inequivalent EBRs for line groups (LG), the symmetry groups of all quasi-1D systems with either translational or helical periodicity. Besides, we determine also EBRs for double-LGs, accounting for spin degree of freedom. In order to illustrate applicability of the results obtained, we analyze electronic-band topology of a chiral single-wall carbon nanotube, using EBRs for relevant (double)-LG and discuss Su-Schrieffer–Heeger model from EBR-perspective.

physica status solidi (RRL) – Rapid Research Letters, 2020

1T'-MoS monolayer is demonstrated to be either a topological semimetal (spinless), or zero-gap se... more 1T'-MoS monolayer is demonstrated to be either a topological semimetal (spinless), or zero-gap semiconductor (spinful, without spin-orbit coupling), or topologically trivial insulator (finite spin-orbit coupling). The latter contradicts a previous prediction that 2 1T'-MoS exhibits quantum-spin Hall (QSH) effect, and the reported value of 2 Z-invariant, calculated from inversion-parity values at four Brillouin-zone high-symmetry points. Namely, as the electronic states of two of these points are double-degenerate and transform according to irreducible representations carrying no parity, the band topology of 2 1T'-MoS is investigated using elementary band representations (EBRs) for layer groups. Novel subroutines which output EBRs and Wilson loop operators for low-dimensional systems are incorporated into POLSym code. Based on the calculated 2 1T'-MoS band structure decomposition onto EBRs of the relevant symmetry group and Wilson loop eigen-spectra, it is revealed that valence-band Wannier functions do not break the symmetry and that Wannier centres are localised within a unit cell. Moreover, the QSH state is proven to be not realisable within 1T'-phase group-VI transition-metal dichalcogenides because EBRs for the relevant symmetry groups are topologically trivial. However, it is predicted that among compounds that form other monoclinic structure, with symmorphic layer group (LG) symmetry, there may exist topologically nontrivial phases, including the QSH state.

Physica E: Low-dimensional Systems and Nanostructures, 2021

Abstract Electron phonon coupling in (quasi)-two-dimensional structures within the first order th... more Abstract Electron phonon coupling in (quasi)-two-dimensional structures within the first order theory is strongly constrained by symmetry, and the resulting deficiencies are manifested in a number of striking phenomena: electronic system dynamically decoupled from lattice, absence of totally symmetric phonons, Jahn-Teller theorem violation (with spontaneous symmetry breaking), insufficiency of the Kohn singularity conditions, nonlinear acoustic branches. Here presented analysis of layered structures enlightens that this phenomena are enforced in highly symmetric structures (including here superconducting CuO2 sheet, atomically thin hexagonal boron nitride, graphene. e.g.). General group theoretical results covering all possible quasi-two-dimensional crystal structures are illustrated on real materials, as well as on a few hypothetical compounds.

The Journal of Physical Chemistry C, 2020

Effects of intrinsic spin-orbit coupling in MoS2 nanotubes are studied for the first time. To thi... more Effects of intrinsic spin-orbit coupling in MoS2 nanotubes are studied for the first time. To this end the double group formalism is applied, yielding model independent information on band/spin spl...

physica status solidi (b), 2016

Raman excitation profiles for homogeneously deformed singlewalled carbon nanotubes are calculated... more Raman excitation profiles for homogeneously deformed singlewalled carbon nanotubes are calculated and systematically analyzed. A number of attractive and apparent effects significant in designing electromechanical devices are caused by torsion and uniaxial strain. The shift of radial breathing mode (RBM) phonon energies due to deformation is negligible. The linear dependence of electronic transition energy shift on deformation is confirmed and it is found that the slope of it is strongly related to the chiral angle of the tube. It is also shown that for some tubes the transition energy shift covers the entire visible-light interval, making them perfectly tunable light absorbers. Two types of deformation are compared, a relaxed (slow) deformation and an adiabatic (fast) one. It is found that transition energies are more sensitive to adiabatic deformation, which can be useful for optomechanical device designing. Raman excitation profile of a (9,9) nanotube under torsion.

arXiv (Cornell University), Aug 26, 2021

All of 320 layer groups, distributed into 80 clusters-single/double ordinary/gray groups-are used... more All of 320 layer groups, distributed into 80 clusters-single/double ordinary/gray groups-are used to complete systematization of linear (in all directions) band crossings and corresponding effective Hamiltonians in high-symmetry Brillouin zone points of layered materials, refining and expanding in literature existing data. Two-and four-dimensional effective Hamiltonians are determined by the allowed (half)integer (co)representations of the same dimension in the crossing point and one-or two-dimensional generic allowed representations. The resulting dispersion types (having isotropic or anisotropic form) are: single cone (with double degenerate crossing point and nondegenerate branches, or 4-fold degenerate crossing point with double degenerate conical branches), poppy-flower (4-fold degenerate crossing point with two pairs of non-degenerate mutually rotated conical branches), and a fortune teller (with nodal lines). Transition to double group, enabling to include spin-orbit interaction, results in various scenarios at high symmetry points: gap closing, gap opening, cone preserving, cone splitting etc. Analogously, analyzing ordinary to gray group transitions, the role of time reversal symmetry is clarified. I. INTRODUCTION Interplay between symmetry and topology of band structures is among the most attractive topics in contemporary condensed matter physics. Besides topological insulators (TIs), nodal semimetals take a notable role, being a material realization of relativistic Dirac, Weyl, and Majorana particles [1-3], or lead to the emergence of unconventional quasiparticles [4-7]. Characterized by band crossings (touching) points (lines) at Fermi level, with energies dispersing linearly, they have various interesting properties: Dirac points represent the interphases between topologically different insulating phases, Weyl points lead to semimetals with chiral anomaly, Fermi arc surface states etc. Protected by crystal symmetries [8-15], these crossing points are robust with respect to various symmetry-preserving perturbations. Energy of the crossing cannot be predicted by symmetry alone; particularly important are those on Fermi level: when placed at (special) high symmetry points (HSPs) in Brillouin zone (BZ), the material is known as a symmetry-enforced semimetal.

Acta Physica Polonica A, Aug 1, 2011

More than fifteen years have passed since the first report of experimental evidence of regularly ... more More than fifteen years have passed since the first report of experimental evidence of regularly coiled carbon nanotubes, but, the structure, formation mechanism and theoretical aspects of these nanotubes still remain unresolved. We propose model of hexagonal, helically coiled single wall carbon nanotubes, determine their line group symmetry and calculate electronic band structure of the relaxed configurations by means of fully symmetry adopted density functional tight binding method implemented into the POLSym code. Electrical properties of the straight and coiled carbon nanotubes of different chiralities are compared and analyzed.

Physica Status Solidi B-basic Solid State Physics, Sep 5, 2014

Thermal conductivity is one of the most interesting physical properties of carbon nanotubes. This... more Thermal conductivity is one of the most interesting physical properties of carbon nanotubes. This quantity has been extensively explored experimentally and theoretically using different approaches like: molecular dynamics simulation, Boltzmann-Peierls phonon transport equation, modified wave-vector model etc. Results of these investigations are of great interest and show that carbon-based materials, graphene and nanotubes in particular, show high values of thermal conductivity. Thus, carbon nanotubes are a good candidate for the future applications as thermal interface materials. In this paper we present the results of thermal conductance  of a model of helically coiled carbon nanotubes (HCCNTs), obtained from phonon dispersion relations. Calculation of  of HCCNTs is based on the Landauer theory where phonon relaxation rate is obtained by simple Klemens-like model.

arXiv (Cornell University), Jun 28, 2023

Vanishing of the total angular momentum of the electrons occupying all orbitals of a closed shell... more Vanishing of the total angular momentum of the electrons occupying all orbitals of a closed shell in an atom is a textbook fact. Understanding the symmetry content of the atomic shell as irreducible representation of angular momentum, enables straightforward transfer of the notion to (translational or helically) periodic systems. More relevant generalizations naturally appear: stratum shell is intermediate step to physically sound band representations, including elementary and basic ones and connected components. We show that nontrivial determinant representation indicates stable topology of band in single colorless layer groups and obstructive limit in in single colorless line groups.

Meeting abstracts, 2012

not Available.

Journal of Physics A: Mathematical and Theoretical

Full sets of inequivalent elementary band co-representations (coEBRs) for spinless and spinful sy... more Full sets of inequivalent elementary band co-representations (coEBRs) for spinless and spinful systems with grey line group (LG) symmetry are calculated and, together with recently reported elementary band representation (EBRs) for colorless single and double LGs by Milošević et al (2020 J. Phys. A: Math. Theor. 53 455204), the task of characterization of nonmagnetic quasi-one-dimensional (quasi-1D) topological crystals by means of the theory of topological quantum chemistry can be completed. Effects of additional time reversal symmetry on band topology and applicability of topological quantum chemistry is thoroughly analyzed. The main conclusions of the latter are illustrated on spinful Su–Schrieffer–Heeger model (topological mirror chain). Technique of induction and decomposition of coEBRs is fully developed and presented in detail. Complete sets of coEBRs for all thirteen families of single and double grey LGs are tabulated. Quasi-1D structures with symmetry enforced hourglass fe...

physica status solidi (b)

Spin-orbit induced phenomena in quasi-one-dimensional systems are analyzed with the help of doubl... more Spin-orbit induced phenomena in quasi-one-dimensional systems are analyzed with the help of double line groups and their irreducible representations. Orbital band splitting and removal of the spin degeneracy are found to be incompatible with vertical mirror symmetry, as well as with simultaneous invariance under the time reversal and horizontal (roto) reflections. This singles out systems with the first and the fifth family line group symmetry as the only candidates for spin polarized currents; direction of electron spin polarization is also determined by the system symmetry. When applied to carbon nanotubes the developed theory enlightens a number of interesting results concerning the band topology and spin polarization of bands.

Acta Crystallographica Section A Foundations and Advances, 2022

Considered are 80 sets of layer groups, each set consisting of four groups: ordinary single and d... more Considered are 80 sets of layer groups, each set consisting of four groups: ordinary single and double, and grey single and double layer groups. The structural properties of layer groups (factorization into cyclic subgroups and the existence of grading according to the sequence of halving subgroups) enable efficient symbolic computation (by the POLSym code) of the relevant properties, real and complex irreducible and allowed (half-)integer (co-)representations in particular. This task includes, as the first step, classification of the irreducible domains based on the group action in the Brillouin zone combined with torus topology. Also, the band (co-)representations induced from the irreducible (co-)representations of Wyckoff-position stabilizers (site-symmetry groups) are decomposed into the irreducible components. These, and other layer group symmetry related theoretical data relevant for physics, layered materials in particular, are tabulated and made available through the web si...

Contemporary Materials, 2016

We studied electron transport in single wall carbon nanotubes placed in stationary homogeneous el... more We studied electron transport in single wall carbon nanotubes placed in stationary homogeneous electric fields, oriented along tubes. Electron distributions for various electric fields are determined by solving stationary multi bands Boltzmann transport equation in presence of electron phonon scattering mechanisms. Contributions of all possible scattering channels, allowed by selection rules and energy conservation, are taken into account for finding scattering rate and collision integrals. As it is previously predicted, large electron drift velocities in straight single wall carbon nanotubes are obtained. Frequent electron scattering as well as low group velocity have strong impact on reduction of drift velocity in helically coiled carbon nanotubes.

Contemporary Materials, 2015

Semiconducting single wall carbon nanotubes (SWCNTs) exhibit high electron mobility in low electr... more Semiconducting single wall carbon nanotubes (SWCNTs) exhibit high electron mobility in low electric field. Tube diameter and temperature have been found to strongly affect transport properties of SWCNTs. We have investigated electron mobility of helically coiled carbon nanotubes (HCCNTs). Electron and phonon band structures of HCCNTs are used in calculation of electron-phonon matrix elements. Scattering rates are calculated using the first order perturbation theory while taking care of energy and momentum conservation law. In order to obtain electron drift velocities, steady state simulation of charge transport is performed using Monte Carlo method.

We show that modified Wigner projector technique and generalized Bloch theorem approach yield max... more We show that modified Wigner projector technique and generalized Bloch theorem approach yield maximally efficient diagonalization of the Hamiltonian of the large symmetrical systems. For the sake of illustration, we perform a case study of the simplified DNA molecule model and solve the energy eigenproblem analytically by using the unit symmetry cell (symcell) and the corresponding low-dimensional subspaces only. Relevant dynamical parameters are automatically obtained, enabling direct interpretation of the result. Effectiveness of the procedure is based on the two key points: (1) replacing infinite sums over the group elements by modified group projectors which are inherently determined by the group generators only; (2) reducing the dynamics of the system (from the infinite dimensional state space) to the low-dimensional symcell subspace, taking the benefit from the induced structure of the state space. Unlike the original Wigner projectors, the modified group projector technique i...

Contemporary Materials, 2016

We studied the stationary electron transport of semiconduction single-wall straight and helically... more We studied the stationary electron transport of semiconduction single-wall straight and helically coiled carbon nanotubes in the presence of electron- phonon interaction. The electron and phonon bands as well as electron phonon coupling matrix elements are obtained from quantum mechanical calculations with the application of symmetry. Total scattering rate for all electronic states relevant for charge transport is obtained as a sum over independent processes. Transport simulation is realized by Monte Carlo algorithm, where free flight time and scattering mechanism are selected randomly. The obtained electron transport properties of helically coiled and straight carbon nanotubes are significantly different. The electron drift velocities in helically coiled nanotubes are several times lower than in straight carbon nanotubes.

Contemporary Materials, 2017

Experimentally is confirmed that helically coiled carbon nanotube (HCCNT) could be used as a smal... more Experimentally is confirmed that helically coiled carbon nanotube (HCCNT) could be used as a small solenoid for generating spatially localized magnetic field. Current distribution during diffusive electronic transport likewise the inductivity of this quantum conductor depends on electric field. Despite slightly lower electron mobility in HCCNTs than that of the straight single wall carbon nanotubes, the coiled nanotubes are attractive for application as nonlinear nano-solenoids. Nonequilibrium electron distribution functions obtained by solving Boltzmann transport equation are used to predict average helical radius of current flow as a function of electric field intensity. Change of spatial distribution of electronic flow with applied electric field is considered and nonlinear inductivity of HCCNT is predicted.

Contemporary Materials, 2014

Thermal conductivity is one of the most interesting physical properties of carbon nanotubes. This... more Thermal conductivity is one of the most interesting physical properties of carbon nanotubes. This quantity has been extensively explored experimentally and theoretically using different approaches like: molecular dynamics simulation, Boltzmann-Peierls phonon transport equation, modified wave-vector model etc. Results of these investigations are of great interest and show that carbon- based materials, graphene and nanotubes in particular, show high values of thermal conductivity. Thus, carbon nanotubes are a good candidate for the future applications as thermal interface materials. In this paper we present the results of thermal conductance s of a model of helically coiled carbon nanotubes (HCCNTs), obtained from phonon dispersion relations. Calculation of s of HCCNTs is based on the Landauer theory where phonon relaxation rate is obtained by simple Klemens-like model.

Journal of Physics A: Mathematical and Theoretical, 2020

Quantized topological invariants characterizing topological phases in quasi-1D materials are usua... more Quantized topological invariants characterizing topological phases in quasi-1D materials are usually considered only on the basis of spatial inversion parity eigenvalues. However, symmetry of quasi-1D systems is far more complex and their complete topological characterisation can be obtained only on the basis of elementary band representations (EBRs) for the relevant symmetry groups. We derive complete sets of inequivalent EBRs for line groups (LG), the symmetry groups of all quasi-1D systems with either translational or helical periodicity. Besides, we determine also EBRs for double-LGs, accounting for spin degree of freedom. In order to illustrate applicability of the results obtained, we analyze electronic-band topology of a chiral single-wall carbon nanotube, using EBRs for relevant (double)-LG and discuss Su-Schrieffer–Heeger model from EBR-perspective.

physica status solidi (RRL) – Rapid Research Letters, 2020

1T'-MoS monolayer is demonstrated to be either a topological semimetal (spinless), or zero-gap se... more 1T'-MoS monolayer is demonstrated to be either a topological semimetal (spinless), or zero-gap semiconductor (spinful, without spin-orbit coupling), or topologically trivial insulator (finite spin-orbit coupling). The latter contradicts a previous prediction that 2 1T'-MoS exhibits quantum-spin Hall (QSH) effect, and the reported value of 2 Z-invariant, calculated from inversion-parity values at four Brillouin-zone high-symmetry points. Namely, as the electronic states of two of these points are double-degenerate and transform according to irreducible representations carrying no parity, the band topology of 2 1T'-MoS is investigated using elementary band representations (EBRs) for layer groups. Novel subroutines which output EBRs and Wilson loop operators for low-dimensional systems are incorporated into POLSym code. Based on the calculated 2 1T'-MoS band structure decomposition onto EBRs of the relevant symmetry group and Wilson loop eigen-spectra, it is revealed that valence-band Wannier functions do not break the symmetry and that Wannier centres are localised within a unit cell. Moreover, the QSH state is proven to be not realisable within 1T'-phase group-VI transition-metal dichalcogenides because EBRs for the relevant symmetry groups are topologically trivial. However, it is predicted that among compounds that form other monoclinic structure, with symmorphic layer group (LG) symmetry, there may exist topologically nontrivial phases, including the QSH state.

Physica E: Low-dimensional Systems and Nanostructures, 2021

Abstract Electron phonon coupling in (quasi)-two-dimensional structures within the first order th... more Abstract Electron phonon coupling in (quasi)-two-dimensional structures within the first order theory is strongly constrained by symmetry, and the resulting deficiencies are manifested in a number of striking phenomena: electronic system dynamically decoupled from lattice, absence of totally symmetric phonons, Jahn-Teller theorem violation (with spontaneous symmetry breaking), insufficiency of the Kohn singularity conditions, nonlinear acoustic branches. Here presented analysis of layered structures enlightens that this phenomena are enforced in highly symmetric structures (including here superconducting CuO2 sheet, atomically thin hexagonal boron nitride, graphene. e.g.). General group theoretical results covering all possible quasi-two-dimensional crystal structures are illustrated on real materials, as well as on a few hypothetical compounds.

The Journal of Physical Chemistry C, 2020

Effects of intrinsic spin-orbit coupling in MoS2 nanotubes are studied for the first time. To thi... more Effects of intrinsic spin-orbit coupling in MoS2 nanotubes are studied for the first time. To this end the double group formalism is applied, yielding model independent information on band/spin spl...

physica status solidi (b), 2016

Raman excitation profiles for homogeneously deformed singlewalled carbon nanotubes are calculated... more Raman excitation profiles for homogeneously deformed singlewalled carbon nanotubes are calculated and systematically analyzed. A number of attractive and apparent effects significant in designing electromechanical devices are caused by torsion and uniaxial strain. The shift of radial breathing mode (RBM) phonon energies due to deformation is negligible. The linear dependence of electronic transition energy shift on deformation is confirmed and it is found that the slope of it is strongly related to the chiral angle of the tube. It is also shown that for some tubes the transition energy shift covers the entire visible-light interval, making them perfectly tunable light absorbers. Two types of deformation are compared, a relaxed (slow) deformation and an adiabatic (fast) one. It is found that transition energies are more sensitive to adiabatic deformation, which can be useful for optomechanical device designing. Raman excitation profile of a (9,9) nanotube under torsion.