Spin transport features of zigzag phosphorene nanoribbons (ZPNRs) are investigated in the presence of the perpendicular electric field ( E z ), the exchange field M , and Rashba spin–orbit interaction (RSOI). To this end, the non-equilibrium Green’s function method is used based on the tight-binding model, which can be described by the Landauer–Büttiker formalism. Interestingly, spin-filtering and spin-flipping are observed only for incoming up (down) spins in the presence of the exchange field with anti-parallel configuration (parallel configuration). Furthermore, changing the magnitude and direction of E z for the parallel and anti-parallel configurations of the exchange field in the presence of RSOI can induce and control the ON/OFF state of the current, the band gap, the spin polarization, spin-flipping, and spin-filtering in the system. The obtained results could be utilized to construct novel nanostructures and also to maximize the efficiency of spintronic devices based on ZPNRs.

This study employed density functional theory calculations to investigate the structural, electronic and magnetic properties of an armchair silicene nanoribbon (ASiNR) substituted with a monomer and a dimer of Fe atom. As a result, the direct band gap of pristine ASiNR turns into a smaller indirect band gap by substituting an Fe atom in the proper position. The magnetic moment of doped Fe reduces and the structure keeps its nonmagnetic property. The substitution of the Fe-dimer can change the pristine ASiNR from a nonmagnetic semiconductor to a magnetic half-metal, which is favorable for spintronic devices. Two external electric fields were applied to the structure substituted with the Fe-dimer and electronic properties were studied in this situation. It was shown that the Fe-dimer substituted ASiNR is such a versatile material that a band gap can be tuned by using an external transverse electric field. Furthermore, the transport properties of these two structures were studied with non-equilibrium Greens function formalism. It is intriguing that single-spin negative differential resistance was observed in the Fe-dimer doped ASiNR.

A crisis in financial markets can be considered as a collective behaviour phenomenon. The collective behaviour is a complex behaviour which exists among a group of animals. The Vicsek model has been adapted to represent this complexity. A unique phase space has been introduced to represent all possible results of the model. The return of the transaction volumes versus the return of the closed price of each share has been used within the defined phase space. The findings show that the direction of the resultant velocity vectors of all share in this phase space act in the same direction when the financial crisis happens. By monitoring the market’s collective behaviour, it will be possible to gain more knowledge about the condition of the market days in crisis. This research aims to investigate the collective behaviour of stocks using the Vicsek model to study the condition of the market during the days in crisis.

We have demonstrated the structural and magnetic properties of small carbon clusters (C _n , n = 2–12) in the framework of collinear approximation using density functional theory. The calculations were performed for amorphous, linear, and ring carbon clusters using full-potential local-orbital method. We have obtained stable structures, total energies, total magnetic moments, and HOMOLUMO energy gap of these clusters. We have found that the amorphous carbon clusters with minimum energy are not magnetic clusters, whereas their less-stable isomers with special configurations are ferromagnetic objects. Two robust magnetic moments were found for C₅ carbon ring (6μ_B) and for pentagonal pyramid C₆ structure (4μ_B).