Landau levels and Shubnikov-de Haas oscillations in monolayer transition metal dichalcogenide semiconductors

We study the Landau level spectrum using a multi-band $\mathbf{k}\cdot\mathbf{p}$ theory in monolayer transition metal dichalcogenide semiconductors. We find that in a wide magnetic field range the Landau levels can be characterized by a harmonic oscillator spectrum and a linear-in-magnetic field term which describes the valley degeneracy breaking. The effect of the non-parabolicity of the band-dispersion on the Landau level spectrum is also discussed. Motivated by recent magnetotransport experiments, we use the self-consistent Born approximation and the Kubo formalism to calculate the Shubnikov de-Haas oscillations of the longitudinal conductivity. We investigate how the doping level, the spin-splitting of the bands and the broken valley degeneracy of the Landau levels affect the magnetoconductance oscillations. Motivated by recent experiments we consider monolayer MoS$_2$ and WSe$_2$ as concrete examples and compare the results of numerical calculations and an analytical formula which is valid in the semiclassical regime. Finally, we briefly analyze the recent experimental results (Reference [18]) using the theoretical approach we have developed

Emergence of bound states in ballistic magnetotransport of graphene antidots

An experimental method for detection of bound states around an antidot formed from a hole in a graphene sheet is proposed by measuring the ballistic two terminal conductances. In particularly, we consider the effect of bound states formed by magnetic field on the two terminal conductance and show that one can observe Breit-Wigner like resonances in the conductance as a function of the Fermi level close to the energies of the bound states. In addition, we develop a new numerical method in which the computational effort is proportional to the linear dimensions, instead of the area of the scattering region beeing typical for the existing numerical recursive Green's function method.Comment: 7 pages, 6 figure

Peculiar Nature of Snake States in Graphene

We study the dynamics of the electrons in a non-uniform magnetic field applied perpendicular to a graphene sheet in the low energy limit when the excitation states can be described by a Dirac type Hamiltonian. We show that as compared to the two-dimensional electron gas (2DEG) snake states in graphene exibit peculiar properties related to the underlying dynamics of the Dirac fermions. The current carried by snake states is locally uncompensated even if the Fermi energy lies between the first non-zero energy Landau levels of the conduction and valence bands. The nature of these states is studied by calculating the current density distribution. It is shown that besides the snake states in finite samples surface states also exist.Comment: 4 pages, 5 figure

Productivity raising approaches in the logistic production system

This paper deals with the productivity of the logistic production system. The aim is to define the intermediate state of the production machines and equipment (OOE), identification of the material flows, idle time and breakdown forecasting, with the following purchase of the required spare parts. The goal of the system is the satisfaction of the customer´s needs and the minimalisation of not fulfilling the required terms for delivery with simultaneous increasing of the logistic production system productivity

Effect of the band structure topology on the minimal conductivity for bilayer graphene with symmetry breaking

Using the Kubo formula we develop a general and simple expression for the minimal conductivity in systems described by a 2×2 Hamiltonian. As an application we derive an analytical expression for the minimal conductivity tensor of bilayer graphene as a function of a complex parameter w related to recently proposed symmetry breaking mechanisms resulting from electron-electron interaction or strain applied to the sample. The number of Dirac points changes with varying parameter w, and this directly affects the minimal conductivity. Our analytic expression is confirmed using an independent calculation based on the Landauer approach, and we find remarkably good agreement between the two methods. We demonstrate that the minimal conductivity is very sensitive to the change of the parameter w and the orientation of the electrodes with respect to the sample. Our results show that the minimal conductivity is closely related to the topology of the low-energy band structure

Non-local Andreev reflection through Andreev molecular states in graphene Josephson junctions

We propose that a device composed of two vertically stacked monolayer graphene Josephson junctions can be used for Cooper pair splitting. The hybridization of the Andreev bound states of the two Josephson junction can facilitate non-local transport in this normal-superconductor hybrid structure, which we study by calculating the non-local differential conductance. Assuming that one of the graphene layers is electron and the other is hole doped, we find that the non-local Andreev reflection can dominate the differential conductance of the system. Our setup does not require the precise control of junction length, doping, or superconducting phase difference, which could be an important advantage for experimental realization.Comment: Main text + supplementar

Proactive approach to smart maintenance and logistics as a auxiliary and service processes in a company

The article describes a proactive approach to smart maintenance and smart logistics. It presents the areas through which all companies must pass. For its successful implementation it is necessary to introduce appropriate management practices also into the area of maintenance. Irrespective of the level of maintenance work in a particular organization, gradual development of maintenance management is needed. The goal is excellent quality of equipment maintenance. The logistics of tomorrow will be supported, to a high extent, by logistics assistance systems. The logistics world is changing - key terms such as Smart Logistics, digitization of the supply chain or Industry 4.0 are widely discussed and already mega trends