NAND/AND/NOT logic gates response in series of mesoscopic quantum rings

There is a special class of logic gates, called universal gates, any one of which is sufficient to express any desired computation. The NAND gate is truly global, given that it is already known, each Boolean function can be represented in a circuit that contains only NOT and AND gates, it is sufficient to show that these gates can be defined from the NAND gate. The effect of Rashba spin-orbit interaction (SOI) on the gate response and spin current density in a series of non-interacting one-dimensional rings connected to some leads is studied theoretically within the waveguide theory. The gates response and spin current density are computed in geometry of the system containing two terminal double quantum rings. Also, the presence and absence of Rashba SOI are treated as the two inputs of the AND/NAND/NOT gates. Furthermore, simulation of the device performance demonstrates that vital improvement toward spintronic applications can be achieved by optimizing device parameters such as magnetic flux and Rashba coefficient.

Download Full-text

SPIN CURRENT INDUCED ELECTRIC FIELD IN A RASHBA QUANTUM WIRE

Modern Physics Letters B ◽

10.1142/s0217984910022718 ◽

2010 ◽

Vol 24 (07) ◽

pp. 649-656

Author(s):

XI FU ◽

GUANGHUI ZHOU

Keyword(s):

Electric Field ◽

Current Density ◽

Quantum Wire ◽

Spin Current ◽

Scattering Matrix ◽

Orbit Coupling ◽

Spin Orbit Coupling ◽

Spin Orbit ◽

Rashba Spin

We investigate theoretically the spin current and spin current induced electric field in a weak Rashba spin-orbit coupling quantum wire (QW) using a definition for spin current by means of scattering matrix. It is found that there exists two non-zero linear spin current density elements which have oscillation peaks at the center of QW and their strengths can be changed by the number of propagation modes and Rashba constant, respectively. Moreover, the spin current induced electric field has also been calculated and its strength is measurable with present technology with which can be used to detect spin current.

Download Full-text

Spin-polarization and spin-dependent logic gates in a double quantum ring based on Rashba spin-orbit effect: Non-equilibrium Green's function approach

Journal of Applied Physics ◽

10.1063/1.4867219 ◽

2014 ◽

Vol 115 (8) ◽

pp. 084307 ◽

Cited By ~ 6

Author(s):

Leila Eslami ◽

Mahdi Esmaeilzadeh

Keyword(s):

Spin Polarization ◽

Green's Function ◽

Logic Gates ◽

Function Approach ◽

Double Quantum ◽

Quantum Ring ◽

Spin Orbit ◽

Rashba Spin ◽

Non Equilibrium Green’S Function ◽

Non Equilibrium

Download Full-text

Spin transport properties in double quantum rings connected in series

Journal of Semiconductors ◽

10.1088/1674-4926/32/2/022001 ◽

2011 ◽

Vol 32 (2) ◽

pp. 022001

Author(s):

Jian Du ◽

Suxin Wang ◽

Jianghong Pan

Keyword(s):

Transport Properties ◽

Spin Transport ◽

Double Quantum ◽

Quantum Rings ◽

In Series

Download Full-text

Analytical study of spin current density and spin-transfer torque in semi-Dirac heterostructures

Journal of Magnetism and Magnetic Materials ◽

10.1016/j.jmmm.2021.168117 ◽

2021 ◽

pp. 168117

Author(s):

Abbas Zarifi ◽

Moslem Zare

Keyword(s):

Current Density ◽

Analytical Study ◽

Spin Current ◽

Spin Transfer Torque ◽

Spin Transfer

Download Full-text

Coupling in concentric double quantum rings

Applied Physics Letters ◽

10.1063/1.2790828 ◽

2007 ◽

Vol 91 (13) ◽

pp. 133116 ◽

Cited By ~ 27

Author(s):

A. Mühle ◽

W. Wegscheider ◽

R. J. Haug

Keyword(s):

Double Quantum ◽

Quantum Rings

Download Full-text

Critique and Improvement of a One-Dimensional Semianalytical Model of a Direct Methanol Fuel Cell

Journal of Fuel Cell Science and Technology ◽

10.1115/1.4006842 ◽

2012 ◽

Vol 9 (5) ◽

Cited By ~ 2

Author(s):

C. C. Kuo ◽

W. E. Lear ◽

J. H. Fletcher ◽

O. D. Crisalle

Keyword(s):

Fuel Cell ◽

Polarization Curve ◽

Current Density ◽

Direct Methanol Fuel Cell ◽

Membrane Electrode Assembly ◽

Membrane Electrode ◽

One Dimensional ◽

Implicit Equation ◽

Direct Methanol ◽

Methanol Fuel Cell

A constructive critique and a suite of proposed improvements for a recent one-dimensional semianalytical model of a direct methanol fuel cell are presented for the purpose of improving the predictive ability of the modeling approach. The model produces a polarization curve for a fuel cell system comprised of a single membrane-electrode assembly, based on a semianalytical one-dimensional solution of the steady-state methanol concentration profile across relevant layers of the membrane electrode assembly. The first improvement proposed is a more precise numerical solution method for an implicit equation that describes the overall current density, leading to better convergence properties. A second improvement is a new technique for identifying the maximum achievable current density, an important piece of information necessary to avoid divergence of the implicit-equation solver. Third, a modeling improvement is introduced through the adoption of a linear ion-conductivity model that enhances the ability to better match experimental polarization-curve data at high current densities. Fourth, a systematic method is advanced for extracting anodic and cathodic transfer-coefficient parameters from experimental data via a least-squares regression procedure, eliminating a potentially significant parameter estimation error. Finally, this study determines that the methanol concentration boundary condition imposed on the membrane side of the membrane-cathode interface plays a critical role in the model’s ability to predict the limiting current density. Furthermore, the study argues for the need to carry out additional experimental work to identify more meaningful boundary concentration values realized by the cell.

Download Full-text

Persistent Spin Current in a Quantum Wire with Weak Rashba Spin–Orbit Coupling

Chinese Physics Letters ◽

10.1088/0256-307x/23/11/050 ◽

2006 ◽

Vol 23 (11) ◽

pp. 3065-3068 ◽

Cited By ~ 7

Author(s):

Wang Yi ◽

Sheng Wei ◽

Zhou Guang-Hui

Keyword(s):

Quantum Wire ◽

Spin Current ◽

Orbit Coupling ◽

Spin Orbit Coupling ◽

Spin Orbit ◽

Rashba Spin

Download Full-text

Pure spin current in a double quantum dot device generated by thermal bias

Journal of Applied Physics ◽

10.1063/1.4803133 ◽

2013 ◽

Vol 113 (16) ◽

pp. 164310 ◽

Cited By ~ 13

Author(s):

X. F. Yang ◽

Y. S. Liu

Keyword(s):

Quantum Dot ◽

Spin Current ◽

Double Quantum ◽

Pure Spin ◽

Double Quantum Dot

Download Full-text

A Numerical Investigation Into the Interaction Between Current Flow and Fuel Consumption in a Segmented-in-Series Tubular SOFC

Journal of Fuel Cell Science and Technology ◽

10.1115/1.3005386 ◽

2009 ◽

Vol 6 (3) ◽

Cited By ~ 1

Author(s):

B. A. Haberman ◽

A. J. Marquis

Keyword(s):

Density Distribution ◽

Fuel Consumption ◽

Current Density ◽

Current Flow ◽

Flow Direction ◽

Ionic Current ◽

Leading Edge ◽

Current Density Distribution ◽

Fuel Flow ◽

In Series

A typical segmented-in-series tubular solid oxide fuel cell (SOFC) consists of flattened ceramic support tubes with rows of electrochemical cells fabricated on their outer surfaces connected in series. It is desirable to design this type of SOFC to operate with a uniform electrolyte current density distribution to make the most efficient use of the available space and possibly to help minimize the onset of cell component degradation. Predicting the electrolyte current density distribution requires an understanding of the many physical and electrochemical processes occurring, and these are simulated using the newly developed SOHAB multiphysics computer code. Of particular interest is the interaction between the current flow within the cells and the consumption of fuel from an adjacent internal gas supply channel. Initial simulations showed that in the absence of fuel consumption, ionic current tends to concentrate near the leading edge of each electrolyte. Further simulations that included fuel consumption showed that the choice of fuel flow direction can have a strong effect on the current flow distribution. The electrolyte current density distribution is biased toward the upstream fuel flow direction because ionic current preferentially flows in regions rich in fuel. Thus the correct choice of fuel flow direction can lead to more uniform electrolyte current density distributions, and hence it is an important design consideration for tubular segmented-in-series SOFCs. Overall, it was found that the choice of fuel flow direction has a negligible effect on the output voltage of the fuel cells.

Download Full-text