TRANSMISSION PROPERTIES OF ELECTRONS IN A T-TYPE OPENED QUANTUM WAVEGUIDE WITH INHOMOGENEOUS MAGNETIC FIELDS

1999 ◽  
Vol 13 (08) ◽  
pp. 903-915 ◽  
Author(s):  
KE-QIU CHEN ◽  
BEN-YUAN GU ◽  
YU-KAE LIN ◽  
D. S. CHUU
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Inhomogeneous Magnetic Field ◽  
Incident Electron Energy ◽  
Mechanical Transmission ◽  
Ballistic Regime ◽  
Quantum Waveguide ◽  
Transmission Coefficients ◽  
Matching Technique ◽  
High Fields

We calculate the quantum-mechanical transmission of electrons in a T-shaped opened quantum waveguide (TOQW) subjected to an inhomogeneous magnetic field perpendicular to the TOQW plane with the use of the mode-matching technique. An electron incident through one branch of the waveguide can travel into the other two channels in the quantum ballistic regime. We find that transmission coefficients in two channels exhibit quite difference from each other and depend sensitively on geometric parameters and magnetic configurations. Sharp peaks with unity amplitude and deep dips are observed in transmission spectrum as a function of the Fermi energy of the incident electrons at some high fields. We also study the variation of transmission with magnetic field and find that the transmission exhibits various patterns such as step drop, deep dips, wide valley, large oscillations, or without any structure, sensitively depending on the incident electron energy and magnetic confinement configurations. It is expected that by applying inhomogeneous magnetic fields to the TOQW with appropriate magnetic configuration one may provide an available way to control transmission property of the TOQW to match practical requirements in devices.

RADIO-FREQUENCY EREAKDOWN CONTROLLED BY DRIFT OF ELECTRONS IN AN INHOMOGENEOUS MAGNETIC FIELD

1961 ◽  
Vol 39 (7) ◽  
pp. 983-992
Author(s):  
L. T. Shepherd ◽  
H. M. Skarsgard
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Radio Frequency ◽  
Inhomogeneous Magnetic Field ◽  
Breakdown Field ◽  
Electron Theory ◽  
Loss Mechanism ◽  
Field Versus ◽  
Average Electron ◽  
The Magnetic Field

A study has been made of r-f. breakdown in which the controlling loss mechanism arises from the drift of electrons in an inhomogeneous magnetic field. The study was carried out using a toroidal system with parallel r-f. electric and steady magnetic fields. An approximate average-electron theory of drift-controlled breakdown is presented. Experimental measurements of breakdown r-f. electric field versus magnetic field were made at various pressures from 1.25 to 6.0 × 10−3 mm of Hg, using hydrogen and helium gases. A radio frequency of 8 Mc/sec was used. Magnetic fields up to 2000 gauss were employed. The r-f. breakdown field was found to vary as the inverse square root of the magnetic field as predicted by the theory.

Rotational structure of triplet–singlet transitions in orthorhombic molecules in intermediate and high magnetic fields

1977 ◽  
Vol 55 (12) ◽  
pp. 1066-1073 ◽  
Author(s):  
C. di Lauro ◽  
E. Perri
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Magnetic Fields ◽  
External Field ◽  
Triplet State ◽  
Rotational Structure ◽  
High Magnetic Fields ◽  
Zero Field ◽  
High Fields

The Zeeman band profiles are calculated for near-case (b) triplet–singlet transitions in asymmetric rotors, making allowance for the intensity perturbations induced by an external magnetic field. It is shown that new bands correlating with zero-field forbidden lines can be observed under the effect of sufficiently high fields. Band profiles and the patterns of the magnetic sublevels of the triplet state split by the external field are discussed in detail for the Paschen–Back limit.

EFFECT OF AN IMPURITY IN THE WIDE-NARROW-WIDE QUANTUM WAVEGUIDE STRUCTURE

2006 ◽  
Vol 20 (16) ◽  
pp. 2283-2294 ◽  
Author(s):  
JIAN-DUO LU ◽  
YI LIN
Keyword(s):  
Numerical Study ◽  
Mechanical Transmission ◽  
Quantum Waveguide ◽  
Impurity Potential ◽  
Absolute Value ◽  
Highly Sensitive ◽  
Matching Technique ◽  
Electron Waveguide ◽  
Dimensional Electron Gas ◽  
Transmission And Reflection

We present a numerical study of the influence of junction-geometries and disorder on quantum-mechanical transmission by considering the presence of an impurity in a wide-narrow-wide (W-N-W) quantum-wire junction. The device is modeled as an electron waveguide of finite cross section. Transmission and reflection probabilities as well as conductance are computed by using model expansions of the wave function together with a waveguide-matching technique. The calculations show that the transmission of the two-dimensional electron gas through the W-N-W geometry is highly sensitive to geometries of junction and can be suppressed by the presence of a repulsive or attractive impurity potential. Furthermore, the depression effect becomes more visible if the absolute value of potential strength becomes bigger.

scholarly journals Dusty Plasma in Inhomogeneous Magnetic Fields in a Stratified Glow Discharge

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 3788
Author(s):  
Elena S. Dzlieva ◽  
Lev G. D’yachkov ◽  
Leontiy A. Novikov ◽  
Sergey I. Pavlov ◽  
Viktor Y. Karasev
Keyword(s):  
Magnetic Field ◽  
Glow Discharge ◽  
Magnetic Fields ◽  
Dusty Plasma ◽  
Inhomogeneous Magnetic Field ◽  
Dust Particles ◽  
Uniform Field ◽  
The Magnetic Field

We study the dynamics of dust particles in a stratified glow discharge in inhomogeneous magnetic fields. Dust structures are formed in standing striations, in which traps for dust particles arise. When a magnetic field is applied, these structures begin to rotate. The observations were carried out in striations near the end of the solenoid, where the region of an inhomogeneous magnetic field begins. With an increase in the magnetic field, the dusty structure can be deformed. The rotation of a dusty structure in an inhomogeneous magnetic field has been studied in detail; it has its own peculiarities in comparison with rotation in a uniform field. We have considered the mechanisms of such rotation and estimated its velocity.

NEUTRON SCATTERING IN MAGNETIC FIELDS UP TO 17 T

2002 ◽  
Vol 16 (20n22) ◽  
pp. 3390-3390
Author(s):  
K. PROKES ◽  
P. SMEIBIDL ◽  
M. MEISSNER
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Neutron Scattering ◽  
Superconducting Magnets ◽  
Superconducting Magnet ◽  
User Program ◽  
Temperature Range ◽  
Sample Position ◽  
High Fields ◽  
Very High

Neutron scattering in magnetic fields can provide important imformation regarding the magnetism of a system under study on microcsopic scale. Although pulse magnets are capable to reach very high fields, for neutron scattering mostly superconducting magnets are used. At present, a split-pair 14.5 T superconducting magnet used for user-program experiments at HMI offers the highest magnetic field for neutron scattering. With Dy-pole tips placed symmetrically around the sample position a 2.5 T enhancement is achieved. The temperature range accessible with such an insert is between 1.8 and 100 K. Temperatures down to 30 mK can be achieved with a dilution stick, which can be inserted into the 14.5 T cryomagnet. In the contribution we report on the latest neutron scattering achievements in magnetic fields obtained at HMI.

Anomalous Collisionless Damping of Alf vén Waves in Inhomogeneous Plasmas

1966 ◽  
Vol 21 (8) ◽  
pp. 1270-1284
Author(s):  
F. Winterberg
Keyword(s):  
Magnetic Field ◽  
Integral Equation ◽  
Magnetic Fields ◽  
Magnetic Field Gradient ◽  
Wave Length ◽  
Collisionless Plasma ◽  
Inhomogeneous Magnetic Field ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Analytic Approximation

It is shown that ALFVÉN waves in a collisionless plasma, permeated by an inhomogeneous magnetic field, are affected by a strong anomalous damping. This anomalous collisionless damping seems to correspond to collision-free LANDAU damping in homogeneous magnetic fields in a similar way as the anomalous viscous and OHMic damping of ALFVÉN waves propagating in inhomogeneous magnetic fields 1 corresponds to the ordinary collisional viscous and OHMic damping of ALFVÉN waves propagating in homogeneous magnetic fields.It is found that the predicted collision-free anomalous damping will obey a law of the form exp{ — (t/τ)2} where the damping time τ depends on the wave-length, the temperature of the plasma, and the magnetic field gradient.Starting from a simplified BOLTZMANN-VLASOV equation, valid for low frequency plasma waves 2, a LAPLACE transform is carried out with regard to the time dependence and an integral equation is derived for the mean plasma velocity. By the faltung theorem this integral equation can be FOURIER transformed into a differential equation for which a W.K.B. solution can be obtained. The inverse transforms can be carried out by making a simple analytic approximation for the W.K.B. solution which is valid over a large range of values.The predicted anomalous damping of ALFVÉN waves is so strong that it may be useful for the purpose of heating a plasma up to high temperatures within a short time.

MAGNETIC FIELDS MODULATED EXTENDED SPIN FIELD EFFECT TRANSISTORS WITH UNPARALLEL FERROMAGNETIC LEADS

2012 ◽  
Vol 27 (02) ◽  
pp. 1350016 ◽  
Author(s):  
YUN-CHANG XIAO ◽  
WEI LUO ◽  
QING-HU ZHONG ◽  
RUI ZHU ◽  
WEN-JI DENG
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Spin Polarization ◽  
Electron Spin ◽  
Field Effect ◽  
Field Effect Transistors ◽  
Numerical Results ◽  
Electron Spin Polarization ◽  
Spin Field ◽  
Transmission Coefficients

Electron spin polarization properties of the Datta–Das spin field effect transistors are studied by taking into account the coexistence of the Rashba and Dresselhaus effects and an in-plane magnetic field. The transistor is connected to ferromagnetic leads with unparallel polarization. Transmission coefficients can be calculated and thus the Landauer–Büttiker conductance are obtained. Numerical results for the spin polarization of the conductance were discussed in detail.

scholarly journals Method for the Estimation of the Limit Coefficients of Reflection and Transition of a Flat Micro Wave in a Bi-complex Medium

2021 ◽  
Vol 5 (1) ◽  
pp. 94-99
Author(s):  
Antim Hristov Yordanov
Keyword(s):  
Magnetic Field ◽  
Dielectric Constant ◽  
Magnetic Fields ◽  
Magnetic Permeability ◽  
Flat Surface ◽  
Complex Medium ◽  
Radio Waves ◽  
Reflection And Transmission ◽  
Transmission Coefficients ◽  
Electric And Magnetic Field

The reaction of different materials to external magnetic fields depends on the frequency of propagation of radio waves in substances and is determined by the dielectric constant, magnetic permeability , by the vectors of the electric and magnetic field. When irradiated with a flat wave on a flat surface, the phenomenon occurs at the boundary between two media, which will be described by an algorithm through reflection and transmission coefficients used in the processing of transmitted and reflected signals from radars, and adopted in radiology as well.

Calculated Coronal Magnetic Fields and Their Comparison with the Coronal Structures as Observed during Five Solar Eclipses

1994 ◽  
Vol 144 ◽  
pp. 559-564
Author(s):  
P. Ambrož ◽  
J. Sýkora
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Coronal Magnetic Field ◽  
Coronal Magnetic Fields ◽  
Solar Eclipses ◽  
Coronal Structures

AbstractWe were successful in observing the solar corona during five solar eclipses (1973-1991). For the eclipse days the coronal magnetic field was calculated by extrapolation from the photosphere. Comparison of the observed and calculated coronal structures is carried out and some peculiarities of this comparison, related to the different phases of the solar cycle, are presented.

Radio Measurements of Coronal Magnetic Fields

1994 ◽  
Vol 144 ◽  
pp. 21-28 ◽  
Author(s):  
G. B. Gelfreikh
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Active Regions ◽  
High Sensitivity ◽  
Coronal Magnetic Field ◽  
Transverse Magnetic ◽  
Radio Sources ◽  
Radio Waves ◽  
Solar Active Regions

AbstractA review of methods of measuring magnetic fields in the solar corona using spectral-polarization observations at microwaves with high spatial resolution is presented. The methods are based on the theory of thermal bremsstrahlung, thermal cyclotron emission, propagation of radio waves in quasi-transverse magnetic field and Faraday rotation of the plane of polarization. The most explicit program of measurements of magnetic fields in the atmosphere of solar active regions has been carried out using radio observations performed on the large reflector radio telescope of the Russian Academy of Sciences — RATAN-600. This proved possible due to good wavelength coverage, multichannel spectrographs observations and high sensitivity to polarization of the instrument. Besides direct measurements of the strength of the magnetic fields in some cases the peculiar parameters of radio sources, such as very steep spectra and high brightness temperatures provide some information on a very complicated local structure of the coronal magnetic field. Of special interest are the results found from combined RATAN-600 and large antennas of aperture synthesis (VLA and WSRT), the latter giving more detailed information on twodimensional structure of radio sources. The bulk of the data obtained allows us to investigate themagnetospheresof the solar active regions as the space in the solar corona where the structures and physical processes are controlled both by the photospheric/underphotospheric currents and surrounding “quiet” corona.

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