Finite-difference method applied for eight-band kp model for Hg1−xCdxTe/HgTe quantum well

2017 ◽  
Vol 31 (20) ◽  
pp. 1750137 ◽  
Author(s):  
Michał Marchewka
Keyword(s):  
Magnetic Field ◽  
Finite Difference ◽  
Finite Difference Method ◽  
Quantum Well ◽  
Quantum Wells ◽  
Difference Method ◽  
Complete Agreement ◽  
Double Quantum ◽  
Multiple Quantum ◽  
Wide Range

In this work the finite-difference method (FDM) is presented for the undoped Hg[Formula: see text]CdxTe/HgTe quantum well (QW) which allows to calculate the band structures based on Kane’s 8 × 8 kp model including all second-order terms representing the remote-band contributions. In particular the common central-difference form is employed in the discretization procedure. The FDM is applied in the envelope function approach (EFA) for the [001]-oriented system for two cases: without a magnetic field ([Formula: see text] = 0) and with a magnetic field perpendicular to the layer ([Formula: see text]). A proposed presented method can solve all the states simultaneously and can be used for a wide range of temperatures and widths of QW for different values of [Formula: see text] for Hg[Formula: see text]CdxTe/HgTe QW as well as for more complex structures, e.g., asymmetric QW, double quantum wells (DQWs), multiple quantum wells (MQWs) and for the so-called 3D topological insulator with a strained HgTe layer. The results obtained by this method are in a complete agreement with the previous ones. Based on that it is shown that the different [Formula: see text]–Cd compounds in the barrier as well as in the QW make the critical width different than 6.4 nm for HgTe QW. What is also very interesting from the application point of view of the strained mixed HgCdTe QW is that for a different width and a different mismatch lattice it is possible to observe the influence of the upper and lower parts of the Dirac cone in, e.g., a magneto-transport experiment.

scholarly journals Flow Past A Rotating Circular Cylinder and A Rotlet Using the Finite-Difference Method

2000 ◽  
Vol 5 ◽  
pp. 85
Author(s):  
T. B. A. El Bashir
Keyword(s):  
Finite Difference ◽  
Finite Difference Method ◽  
Circular Cylinder ◽  
Difference Method ◽  
General Nature ◽  
Rotational Parameter ◽  
Rotating Circular Cylinder ◽  
Analytical Results ◽  
Wide Range ◽  
The Finite Difference Method

In this paper the flow generated by a rotlet in the presence of a circular cylinder is considered. We introduce a transformation which simplifies the equations and boundary conditions. We use the finite-difference method to obtain results in excellent agreement with all the available analytical results. Results are presented for Reynolds numbers, based on the diameter of the cylinder, in the range 0 ≤ Re ≤ 20 and the rotational parameter, α , in the range 0 ≤α ≤ 3 and strength of rotlet, β , in the range 0 ≤ β ≤ 3 . The results are found to be applicable over a wide range of values of α and β . The calculated values of the drag, lift and moment coefficients and the general nature of the streamline patterns are in good agreement with analytical results . The method is then utilized to obtain new results for which no analytical solution is possible.

scholarly journals Thermal Radiation Effects on Hydromagnetic Mixed Convection Flow along a Magnetized Vertical Porous Plate

2010 ◽  
Vol 2010 ◽  
pp. 1-30 ◽  
Author(s):  
Muhammad Ashraf ◽  
S. Asghar ◽  
Md. Anwar Hossain
Keyword(s):  
Magnetic Field ◽  
Finite Difference ◽  
Finite Difference Method ◽  
Prandtl Number ◽  
Mixed Convection ◽  
Difference Method ◽  
Porous Plate ◽  
Physical Parameters ◽  
Local Skin ◽  
Vertical Porous Plate

Aim of the present work is to investigate the effect of radiation on steady mixed convection boundary layer flow of viscous, incompressible, electrically conducting fluid past a semi-infinite magnetized vertical porous plate with uniform transpiration and variable transverse magnetic field along the surface. The equations governing the flow magnetic and temperature field are reduced to dimensionless convenient form using the free variable transformations and solved numerically by using finite difference method. Effects of physical parameters like Prandtl number, Pr, the conduction-radiation parameterRd, magnetic field parameterS, magnetic Prandtl numberPm, mixed convection parameterλ, and the surface temperature,θwon the local skin friction coefficientCfx, local Nusselt number,Nux, and coefficient of magnetic intensity,Mgxagainst the local transpiration parameterξare shown graphically. Later, the problem is analysed by using series solution for small and large values ofξ, and the results near and away from the leading edge are compared with numerical results obtained by finite difference method and found to be in good agreement.

MOCVD Growth and Characterization of GaInNAs/GaAs/InGaAs/GaAs Quantum Well Structures

2002 ◽  
Vol 744 ◽  
Author(s):  
Abdel-Rahman A. El-Emawy ◽  
Hongjun Cao ◽  
Noppadon Nuntawong ◽  
Chiyu Liu ◽  
Marek Osiński
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Growth Parameters ◽  
Multiple Quantum Well ◽  
Double Quantum ◽  
Multiple Quantum ◽  
Quantum Well Structures ◽  
Mocvd Growth ◽  
Double Quantum Well ◽  
Wavelength Emission

ABSTRACTEffects of MOCVD growth parameters on structural and optical properties of double-quantum-well (DQW) structures containing uncoupled GaInNAs/GaAs and InGaAs/GaAs quantum wells have been investigated. By varying growth temperature, growth rate, V/III ratio, and DMHy flow rates, we have achieved a longer-wavelength emission from a GaInNAs well than from an InGaAs well grown in the same structure. GaInNAs/GaAs multiple-quantum-well structures grown under optimum conditions emitted at 1.25 μm.

GIANT INCREASE OF THE EXCITON LIFETIME IN SEMIMAGNETIC SEMICONDUCTORS WITH DOUBLE QUANTUM WELLS IN MAGNETIC FIELD

2004 ◽  
Vol 03 (04n05) ◽  
pp. 541-547
Author(s):  
I. Yu. GOLINEY ◽  
S. B. LEV ◽  
V. I. SUGAKOV ◽  
G. V. VERTSIMAKHA
Keyword(s):  
Magnetic Field ◽  
Quantum Well ◽  
Quantum Wells ◽  
Double Quantum ◽  
Quantum Well Structures ◽  
Indirect Exciton ◽  
Exciton Lifetime ◽  
Double Quantum Well ◽  
Single Well ◽  
Semimagnetic Semiconductors

Magnetic field dependence of the excitonic spectrum and the intensity of the optical transitions for excitons in the double quantum well heterostructures based on semimagnetic semiconductors of various compositions are studied. The calculations carried out for (Zn, Mn)Se -based double quantum well structures showed that in the weak magnetic fields, the lowest energy states are the single-well states (direct excitons) for which both the electron and the hole are predominantly localized in the same well. At some values of magnetic field, the crossing of the direct exciton with indirect exciton formed by an electron and a hole, situated predominantly in the different wells, occurs. In the magnetic field exceeding some critical value, the lowest energy level belongs to the indirect exciton. According to the estimates, the lifetime of the indirect exciton is by several orders of magnitude larger than that of a single-well exciton. The exciton lifetime depends significantly on the width and the material of the barrier between the wells.

Effect of Turbulence and Offset Loading on the Performance of a Single Pad Externally Adjustable Fluid Film Bearing

2012 ◽  
Author(s):  
B. Satish Shenoy ◽  
Rammohan S. Pai B. ◽  
Raghuvir Pai B. ◽  
Shrikanth Rao D.
Keyword(s):  
Steady State ◽  
Finite Difference ◽  
Aspect Ratio ◽  
Finite Difference Method ◽  
Difference Method ◽  
Reynolds Equation ◽  
Load Capacity ◽  
Fluid Film ◽  
Wide Range ◽  
Steady State Performance

Paper deals with the effect of turbulence on steady state performance characteristics of an eccentrically loaded 120° single pad externally adjustable fluid film bearing. The bearing has an aspect ratio of one and operates over a wide range of eccentricity ratios and adjustments. Two load-offset positions (β/χ) of 0.45 and 0.55 are considered in the present analysis. Reynolds equation incorporated with the Linearized turbulence model of Ng and Pan is solved numerically using finite difference method. A comparative study predicts that, load capacity of a bearing operating with β/χ = 0.55 and Re = 16000 is superior for negative radial and tilt adjustment configuration of the pad.

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