Magnetooptical Studies of Acceptors Confined in GaAs/AIGaAs Quantum Wells

1993 ◽  
Vol 325 ◽  
Author(s):  
P.O. Holtz ◽  
Q.X. Zhao ◽  
B. Monemar ◽  
A. Pasquarello ◽  
M. Sundaram ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Quantum Wells ◽  
Ground State ◽  
Energy Levels ◽  
Zeeman Splitting ◽  
Growth Direction ◽  
Bulk Gaas ◽  
Theoretical Predictions ◽  
Resonant Raman ◽  
The Magnetic Field

AbstractMagnetooptical studies have been performed on the shallow Be acceptor confined in the central region of narrow GaAs/AlGaAs quantum wells (QWs) with the magnetic field along the growth direction. The magnetic field dependence of the acceptor transition between the 1S(Г6) hh-like ground state and the excited hh-like 2S(Г6) state has been investigated by means of two independent techniques: Two-hole transitions of the acceptor bound exciton (BE) and resonant Raman scattering. The 1S(Г6) – 2S(Г6) transition energy as a function of the magnetic field has been measured for central acceptors in QWs of widths in the range 50 – 150 Å. The energy levels for the 1S ground states and 2S excited states of the confined acceptor with a magnetic field as a perturbation have also been calculated. These calculations predict a larger splitting between the mj=+3/2 and mj=−3/2 components of the acceptor 1S(Г6) ground state in comparison with the corresponding splitting of the excited 2S(Г6) state. The experimental results are in good agreement with the theoretical predictions derived without any fitting parameters. Furthermore, the Zeeman splitting of the acceptor BE emission has been measured and it is concluded that the J = 5/2 BE state is lowest in energy, similar to shallow acceptor BEs in bulk GaAs.

VALLEY SPLITTING AND g-FACTOR IN AlAs QUANTUM WELLS

2009 ◽  
Vol 23 (12n13) ◽  
pp. 2948-2954
Author(s):  
C. A. DUARTE ◽  
G. M. GUSEV ◽  
T. E. LAMAS ◽  
A. K. BAKAROV ◽  
J.-C. PORTAL
Keyword(s):  
Magnetic Field ◽  
Quantum Wells ◽  
Quantum Confinement ◽  
Zeeman Splitting ◽  
Exchange Contribution ◽  
G Factor ◽  
Valley Splitting ◽  
Perpendicular Component ◽  
Magneto Resistance ◽  
The Magnetic Field

Here we present the results of magneto resistance measurements in tilted magnetic field and compare them with calculations. The comparison between calculated and measured spectra for the case of perpendicular fields enable us to estimate the dependence of the valley splitting as a function of the magnetic field and the total Landé g -factor (which is assumed to be independent of the magnetic field). Since both the exchange contribution to the Zeeman splitting as well as the valley splitting are properties associated with the 2D quantum confinement, they depend only on the perpendicular component of the magnetic field, while the bare Zeeman splitting depends on the total magnetic field. This information aided by the comparison between experimental and calculated gray scale maps permits to obtain separately the values of the exchange and the bare contribution to the g -factor.

scholarly journals Effect of magnetic field and impurities in InAs/GaAs and GaN/AlN self-assembled quantum dots

2019 ◽  
Vol 65 (3) ◽  
pp. 231
Author(s):  
G. Linares García ◽  
And L. Meza-Montes
Keyword(s):  
Magnetic Field ◽  
Quantum Dots ◽  
Probability Density ◽  
Electronic States ◽  
Zeeman Splitting ◽  
Growth Direction ◽  
Two Systems ◽  
Piezoelectric Effects ◽  
Self Assembled ◽  
The Magnetic Field

A theoeritical study on the effect of a magnetic field or impurities on the carries states of self-assembled quantum dots is presented. The magnetic field is applied along the growth direction of the dots, and for comparison two systems are considered, InAs embeded in GaAs, and GaN in AlN. The electronic states and energy are calculated in the framework of the k.p theory in 8 bands including the strain and piezoelectric effects. Zeeman splitting and anticrossings are observed in InAs/GaAs, while the field introduces small changes in the nitrides. It is also included a study about hidrogen-like impurities, which may be negative or positive. It is noted that depending on the type of impurity, the confinement energy of carriers is changed, and the distribution of the probability density of the carriers is affected  too.

Carrier Pocket Engineering to Design Superior Thermoelectric Materials Using GaAs/AlAs Superlattices

1998 ◽  
Vol 545 ◽  
Author(s):  
T. Koga ◽  
X. Sun ◽  
S. B. Cronin ◽  
M. S. Dresselhaus
Keyword(s):  
Quantum Wells ◽  
Figure Of Merit ◽  
Growth Direction ◽  
Present Calculation ◽  
High Symmetry ◽  
Thermoelectric Figure ◽  
Bulk Gaas ◽  
Basic Model ◽  
Short Period ◽  
Superlattice Period

AbstractA large enhancement in the thermoelectric figure of merit for the whole superlattice, Z3DT, is predicted for short period GaAs/AlAs superlattices relative to bulk GaAs. Various superlattice parameters (superlattice growth direction, superlattice period and layer thicknesses) are explored to optimize Z3DT, including quantum wells formed at various high symmetry points in the Brillouin zone. The highest room temperature Z3DT obtained in the present calculation is 0.41 at the optimum carrier concentration for either (001) or (111) oriented GaAs(20 Å)/AIAs(20 Å) superlattices, which is about 50 times greater than the corresponding ZT for bulk GaAs obtained using the same basic model.

scholarly journals The magnetic field in the dense photodissociation region of DR 21

2020 ◽  
Author(s):  
Atanu Koley ◽  
Nirupam Roy ◽  
Karl M Menten ◽  
Arshia M Jacob ◽  
Thushara G S Pillai ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Zeeman Effect ◽  
Zeeman Splitting ◽  
Weak Field ◽  
Field Energy ◽  
Evolutionary Stage ◽  
Maser Emission ◽  
The Magnetic Field ◽  
Photodissociation Region

Abstract Measuring interstellar magnetic fields is extremely important for understanding their role in different evolutionary stages of interstellar clouds and of star formation. However, detecting the weak field is observationally challenging. We present measurements of the Zeeman effect in the 1665 and 1667 MHz (18 cm) lines of the hydroxyl radical (OH) lines toward the dense photodissociation region (PDR) associated with the compact H ii region DR 21 (Main). From the OH 18 cm absorption, observed with the Karl G. Jansky Very Large Array, we find that the line of sight magnetic field in this region is ∼0.13 mG. The same transitions in maser emission toward the neighbouring DR 21(OH) and W 75S-FR1 regions also exhibit the Zeeman splitting. Along with the OH data, we use [C ii] 158 μm line and hydrogen radio recombination line data to constrain the physical conditions and the kinematics of the region. We find the OH column density to be ∼3.6 × 1016(Tex/25 K) cm−2, and that the 1665 and 1667 MHz absorption lines are originating from the gas where OH and C+ are co-existing in the PDR. Under reasonable assumptions, we find the measured magnetic field strength for the PDR to be lower than the value expected from the commonly discussed density–magnetic field relation while the field strength values estimated from the maser emission are roughly consistent with the same. Finally, we compare the magnetic field energy density with the overall energetics of DR 21’s PDR and find that, in its current evolutionary stage, the magnetic field is not dynamically important.

scholarly journals Energy Correlations of α-Particles in the 8Be-Nucleus Ground-State Formation Channel of the 12C(γ,3α) and 16O(γ,4α) Reactions

2019 ◽  
Vol 64 (9) ◽  
pp. 787
Author(s):  
S. N. Afanasyev
Keyword(s):  
Magnetic Field ◽  
Photon Energy ◽  
Relative Motion ◽  
Cross Sections ◽  
Ground State ◽  
Diffusion Chamber ◽  
Mechanism Of Interaction ◽  
The Magnetic Field ◽  
Maximum Photon ◽  
Α Particles

The method of diffusion chamber in the magnetic field making use of a bremsstrahlung beam with a maximum photon energy of 150 MeV is applied to study the 12C(y,3a) and 16O(y,4a) reactions. A resonance identified as the ground state of 8Be nucleus is found in the distribution of events over the energy of the relative motion of two a-particles. The partial cross-sections of the 8Be nucleus formation channels are measured. It is shown that the mechanism of interaction between a y-quantum and a virtual a-particle pair takes place in this case.

scholarly journals Spin-1/2 Particles under the Influence of a Uniform Magnetic Field in the Interior Schwarzschild Solution

Universe ◽  
2021 ◽  
Vol 7 (12) ◽  
pp. 467
Author(s):  
Fayçal Hammad ◽  
Alexandre Landry ◽  
Parvaneh Sadeghi
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Total Mass ◽  
Uniform Magnetic Field ◽  
Energy Levels ◽  
Relativistic Wave Equation ◽  
Relativistic Wave ◽  
Schwarzschild Solution ◽  
Relativistic Regime ◽  
The Magnetic Field

The relativistic wave equation for spin-1/2 particles in the interior Schwarzschild solution in the presence of a uniform magnetic field is obtained. The fully relativistic regime is considered, and the energy levels occupied by the particles are derived as functions of the magnetic field, the radius of the massive sphere and the total mass of the latter. As no assumption is made on the relative strengths of the particles’ interaction with the gravitational and magnetic fields, the relevance of our results to the physics of the interior of neutron stars, where both the gravitational and the magnetic fields are very intense, is discussed.

The influences of parabolic potential and magnetism on strongly coupled polaron characteristics within asymmetric Gaussian quantum wells

2021 ◽  
Author(s):  
Saren Gaowa ◽  
Yan-Bo Geng ◽  
Zhao-Hua Ding ◽  
Jing-Lin Xiao
Keyword(s):  
Magnetic Field ◽  
Quantum Wells ◽  
Barrier Height ◽  
Ground State Energy ◽  
Ground State ◽  
State Energy ◽  
Cyclotron Frequency ◽  
Strongly Coupled ◽  
Parabolic Potential ◽  
Do So

In this research, the effects of magnetism and parabolic potential on strongly coupled polaron characteristics within asymmetric Gaussian quantum wells (AGQWs) were investigated. To do so, the following six parameters were studied, temperature, AGQW barrier height, Gaussian confinement potential (GCP) width, confinement strengths along the directions of [Formula: see text] and [Formula: see text], as well as magnetic field cyclotron frequency. The relationships among frequency oscillation, AGQW parameters and polaron ground state energy in RbCl crystal were studied based on linear combination operator and Lee–Low–Pines unitary transformation. It was concluded that ground state energy absolute value was decreased by increasing GCP width and temperature, and increased with the increase of confinement strength along [Formula: see text] and [Formula: see text] directions, cyclotron frequency of magnetic field and barrier height of AGQW. It was also found that vibrational frequency was increased by enhancing confinement strengths along the directions of [Formula: see text] and [Formula: see text], magnetic field cyclotron frequencies, barrier height AGQW and temperature and decreased with the increase of GCP width.

scholarly journals The Magnetic Field Near the Local Bubble

1997 ◽  
Vol 166 ◽  
pp. 227-238
Author(s):  
Carl Heiles
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Zeeman Splitting ◽  
Relativistic Electrons ◽  
Local Bubble ◽  
Scale Field ◽  
Large Scale Field ◽  
Field Lines ◽  
Hi Shells ◽  
The Magnetic Field

AbstractThere are almost no direct observational indicators of the magnetic field inside the local bubble. Just outside the bubble, the best tracers are stellar polarization and HI Zeeman splitting. These show that the local field does not follow the large-scale Galactic field. Here we discuss whether the deformation of the large-scale field by the local HI shells is consistent with the observations. We concentrate on the Loop 1 region, and find that the field lines are well-explained by this idea; in addition, the bright radio filaments of Radio Loop 1 delineate particular field lines that are “lit up” by an excess of relativistic electrons.

scholarly journals Spin Polarization Oscillations and Coherence Time in the Random Interaction Approach

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
P. Pereyra
Keyword(s):  
Magnetic Field ◽  
Time Evolution ◽  
Spin Polarization ◽  
Energy Levels ◽  
Coherence Time ◽  
Environment Interaction ◽  
Interaction Picture ◽  
Gaussian Orthogonal Ensemble ◽  
Interaction Approach ◽  
The Magnetic Field

We study the time evolution of the survival probability and the spin polarization of a dissipative nondegenerate two-level system in the presence of a magnetic field in the Faraday configuration. We apply the Extended Gaussian Orthogonal Ensemble approach to model the stochastic system-environment interaction and calculate the survival and spin polarization to first and second order of the interaction picture. We present also the time evolution of the thermal average of these quantities as functions of the temperature, the magnetic field, and the energy-levels density, for ρ(ϵ)∝ϵs, in the subohmic, ohmic, and superohmic dissipation forms. We show that the behavior of the spin polarization calculated here agrees rather well with the time evolution of spin polarization observed and calculated, recently, for the electron-nucleus dynamics of Ga centers in dilute (Ga,N)As semiconductors.

Sign in / Sign up

Export Citation Format

Share Document