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The transmission properties of armchair- and zigzag-edged graphene nanoribbon junctions between graphene electrodes are examined by means of the standard nonequilibrium Green’s function (NEGF) technique. The quantum transport of electrons is studied through a monolayer graphene strip in the presence of Rashba spin–orbit coupling that acts as a barrier between the two normal leads. The present work compares the conductances of nanoribbons with zigzag and armchair edges. Since the nature of induced gap for zigzag edge is different from armchair, it is expected to give rise to different types of conductance for each edge. Findings indicate that the Rashba strength has more pronounced influence on armchair ribbons than on zigzag ribbons, and the minimum conductance of $2G_0$ for nanoribbon remains intact even in the presence of the Rashba spin–orbit coupling. It is predicted that controllability of spin transport in the monolayer graphene may contribute to the development of well-known spintronics.

The stability of the existence of the topological properties even in non-equilibrium condition such as irradiation of external time-periodic perturbation paves the way for designing and controlling the properties of materials. We study the change in the structure of the quasi-energy spectrum under the influence of the circularly polarized laser field with various intensities. The system is two-dimensional honeycomb nanoribbon of having zig-zag edges. Two cases where the onsite energies are present and absent are considered. We find that the topological phase transitions occur at some critical intensities of the laser field in both cases, which are recognized by the gap closing, the appearance of two crossing edge states, and sudden raise of the first Chern number from 0 to 1. The critical laser intensity is raised when either the frequency increases or the width of the ribbon decreases. Furthermore, band folding is observed in low-frequency domain in the quasi-energy spectrum and becomes more pronounced for the lower frequencies.

Possibility of having different topological phases by time-periodic external field encourages people who wish to manipulate the properties of the materials as their will for the various kinds of systems including a honeycomb nanoribbon. We study bulk-edge correspondence by looking at the change in the value of the first Chern number of a specific band, which reflects the bulk properties, together with the change of associated edge states in quasienergy spectrum when the honeycomb nanoribbon is exposed to circularly polarized laser field. Various topological phase transitions are observed as the intensity of the laser field is raised up and we classify them in two categories. In the first category, when the frequency is sufficiently high, the system undergoes simple transition from trivial phase to topological one, reflected by the sudden jump in the value of Chern number from 0 to 1 and the appearance of two crossing edge states in the spectrum. Whereas, in the second category where the frequency is low enough, anomalous transitions are drawn, having several nonzero values of Chern number, and band folding prevails, often disappearing depending on the laser intensities. The results confirm the bulk-edge correspondence in periodically driven systems and will contribute to future material designs.

We present two compact analytic formulae for calculating the channel number in graphene nanoribbons (GNRs), in terms of GNRs' width and Fermi energy. Numerical data obtained from these analytic formulae fit those obtained numerically from the exact formula, with accuracies within 1%. Using appropriate fit parameters, the compact formulae are valid for zigzag, armchair-metallic, and armchair-semiconducting GNRs, at room, liquid nitrogen, and liquid helium temperatures (i.e. 300, 77 and 4.2 K)

By performing density functional theory (DFT) calculations, we demonstrate that periodically repeating heterostructures of zigzag borophene nanoribbons (BNR) of different widths can form stable borophene superlattice (BSL). The energy band structures of BSL can be modulated through modifying the width and length of the segments. A metal-semiconductor transition can be obtained when the length of each segment is lengthened, whereas, the magnetism of BSL is influenced by the width of the segments. In those magnetic systems, the magnetic moments are mainly localized on protruding B atoms located at the edge, while no magnetic moments occur in the center B atoms. The hydrogenated BNR and BSL are further investigated. The hydrogenation can modify the electronic properties of BNR and BSL as well as quench the magnetism. All hydrogenated BNR and BSL are non-magnetic. Our results indicate that great potential exists in these systems for borophene utilization in nanoelectronics and spintronics.

The electronic properties of zigzag and armchair SiC nanoribbons are studied using a theoretical method. The spin-unrestricted electronic behavior of an armchair and zigzag SiC nanoribbon containing Si and C vacancy in the supercell was investigated. Spin-polarized electronic structure calculations show that armchair SiC nanoribbon was classified as a nonmagnetic semiconductor while zigzag SiC nanoribbon presents a half-metallic electronic structure. Our results suggest that SiC nanoribbon containing point vacancy may be a good candidate for spintronics due to its half-metal properties.

In this study, the electronic and magnetic properties of hydrogen-passivated armchair and zigzag GaN nanoribbons are investigated using density-functional theory. We explore that doped TM atom leads to additional levels in the band gap and thus plays an essential role in spin polarization and changes their properties. Depending on its location in the nanoribbon, the character of spin-dependent electronic property of a doped GaN-NR was analyzed. Our calculations show that, regardless of the position of Mn atoms, GaNNTs are stable in ferromagnetic phase.

The electronic transport property and band structure of pure gallium nitride, oxygen, fluorine, indium substituted gallium nitride nanoribbon and defect structured GaN nanoribbons are investigated by employing first-principles studies using density functional theory. The band structure of pure GaN and indium substituted GaN nanoribbon shows a semiconducting nature. The oxygen, fluorine substituted GaN and defect structured GaN results in metallic behavior. The density of states provides the insight for the localization of charges in the valence band and conduction band. The substitution of oxygen and fluorine enhance the density of charges in valence band and conduction band. The substitution of indium shows an increase in the peak amplitude in density of states. The presence of defect also increases the density of states. The transport properties are studied in terms of transmission spectrum; pure GaN and indium substituted shows a same trend in transmission. In contrast, the transmission can be enhanced by the substitution of oxygen, fluorine and defect in nanoribbon. The information provided in the present study will pave its way to tailor a new material of GaN nanostructures with improved performance in the optoelectronic devices.

Well-crystallized Na_0.44MnO₂ is readily synthesized via a facile NaCl-flux reaction at 850°C for 5 h. The Na_0.44MnO₂ material exhibits a well-defined nanoribbon structure with dimension of 50–100 nm in thickness and 200–500 nm in width. Electrochemical properties of as-prepared Na_0.44MnO₂ are thoroughly investigated on assembled nonaqueous Na_0.44MnO₂//Na cells using cyclic voltammetry, galvanostatic test, and electrochemical impedance spectroscopy. The results show that the Na_0.44MnO₂ nanoribbon material can deliver a high capacity of 106 mAh g^-1 with stable cycling performance over 40 cycles. In addition, it exhibits a favorable rate capability, delivering a capacity of 90 mAh g^-1 at a rate of 1 C. The high capacity retention combined with acceptable rate capability makes the Na_0.44MnO₂ a promising electrode material for advanced Na-ion batteries.