Effect Of In-plane Magnetic Field Research Articles

Diamagnetic contribution to the effect of in-plane magnetic field on a quantum-dot exciton fine structure

We examine the diamagnetic contribution to the effect of an in-plane magnetic field on the excitonic fine structure in quantum dots. Magnetic compression of the wave function in the direction perpendicular to the field modifies the long-range exchange interaction and can contribute to cancellation of the anisotropic exchange splitting. Numerical estimates indicate that this orbital effect can be comparable with the Zeeman spin effect and should play a significant role in usual experimental configurations.

Exciton diamagnetic shift in [formula omitted] quantum wells under in-plane magnetic fields

Using a variational procedure in the effective-mass and parabolic-band approximations we investigate the effects of in-plane magnetic fields on the exciton states in single GaAs/Ga1-xAlxAs quantum wells. Exciton properties are analyzed by using a simple hydrogen-like variational envelope wave-function. Present theoretical results are compared with available experimental measurements on the diamagnetic shift of the photoluminescence peak position of GaAs/Ga0.7Al0.3As quantum wells under in-plane magnetic fields [Phys. Rev. B 71 (2005) 045303].

Anisotropic Transport of Two-Dimensional Hole System in Higher Landau Levels: Effect of In-Plane Magnetic Field

We have observed anisotropic states of two-dimensional hole systems (2DHS) in higher Landau levels which are analogous to those found in 2D electron systems (2DES), the so-called stripe phase. Application of in-plane magnetic field along the hard (high resistance) direction stabilizes the anisotropic state, while that along the easy axis hardly affect the state. This is in contrast to the corresponding 2DES case where the stripe is easily reoriented by an in-plane magnetic field, and suggests that the built-in symmetry-breaking cause which favors a particular stripe orientation acts more strongly in 2DHS than in 2DES. We discuss the possible origin of the orientational pinning.

Effects of in-plane magnetic fields on the electronic cyclotron effective mass and Landé factor in GaAs-(Ga,Al)As quantum wells

The dependence of the electron Lande g-factor on carrier confinement in quantum wells recently gained both experimental and theoretical interest. The g factor of electrons in GaAs-(Ga,Al)As quantum wells is of special interest, as it changes its sign at a certain value of the well width. In the present work, the effects of an in-plane magnetic field on the cyclotron effective mass and on the Lande g^-factor in single GaAs-(Ga,Al)As quantum wells are studied. Theoretical calculations are performed in the framework of the effective-mass and non-parabolic-band approximations. The Ogg-McCombe Hamiltonian is used for the conduction-band electrons in the semiconductor heterostructure, and the Lande g^-factor theoretically evaluated is found in good agrement with available experimental measurements.

Self-similarity and anti-self-similarity of the effective Landég⊥factor inGaAs−(Ga,Al)AsFibonacci superlattices under in-plane magnetic fields

A theoretical study of the effects of in-plane magnetic fields on the Land\'e ${g}_{\ensuremath{\perp}}$ factor associated to conduction electrons in $\mathrm{GaAs}\text{\ensuremath{-}}(\mathrm{Ga},\mathrm{Al})\mathrm{As}$ Fibonacci superlattices is presented. We have used the Ogg-McCombe effective Hamiltonian, which includes nonparabolic and anisotropy effects, in order to describe the electron states in the Fibonacci heterostructure. We have expanded the corresponding electron envelope wave functions in terms of harmonic-oscillator wave functions, and obtained the Land\'e ${g}_{\ensuremath{\perp}}$ factor for magnetic fields related by even powers of the golden mean $\ensuremath{\tau}=(1+\sqrt{5})∕2$. Theoretical results for $\mathrm{GaAs}\text{\ensuremath{-}}(\mathrm{Ga},\mathrm{Al})\mathrm{As}$ Fibonacci superlattices, under magnetic-field values scaled by ${\ensuremath{\tau}}^{2n}$, clearly exhibit a self-similar (for even $n$) or anti-self-similar (for odd $n$) behavior for the Land\'e ${g}_{\ensuremath{\perp}}$ factors, as appropriate.

Pinned bilayer Wigner crystals with pseudospin magnetism

We study a model of pinned bilayer Wigner crystals (WC) and focus on the effects of interlayer coherence (IC) on pinning. We consider both a pseudospin ferromagnetic WC (FMWC) with IC and a pseudospin antiferromagnetic WC (AFMWC) without IC. Our central finding is that a FMWC can be pinned more strongly due to the presence of IC. One specific mechanism is through the disorder induced interlayer tunneling, which effectively manifests as an extra pinning in a FMWC. We also construct a general ``effective disorder'' model and effective pinning Hamiltonian for the case of FMWC and AFMWC respectively. Under this framework, pinning in the presence of IC involves interlayer spatial correlation of disorder in addition to intralayer correlation, leading to enhanced pinning in the FMWC. The pinning mode frequency $({\ensuremath{\omega}}_{\mathrm{pk}})$ of a FMWC is found to decrease with the effective layer separation, whereas for an AFMWC the opposite behavior is expected. An abrupt drop of ${\ensuremath{\omega}}_{\mathrm{pk}}$ is predicted at a transition from a FMWC to AFMWC. Possible effects of in-plane magnetic fields and finite temperatures are addressed. Finally we discuss some other possible ramifications of the FMWC as an electronic supersolid-like phase.

Effects of non-parabolicity and in-plane magnetic fields on the cyclotron effective mass andg⊥-factor in GaAs-(Ga,Al)As quantum wells

The envelope-function approach is used to theoretically study the effects of in-plane magnetic fields on the cyclotron effective mass and Land\'e ${g}_{\ensuremath{\perp}}$-factor associated to conduction electrons in single GaAs-(Ga,Al)As quantum wells. Non-parabolic and anisotropy effects are included in the calculations within the Ogg-McCombe effective Hamiltonian to describe the electron states in the semiconductor heterostructure. The electronic structure and both the cyclotron effective mass and Land\'e ${g}_{\ensuremath{\perp}}$-factor were obtained, by expanding the corresponding envelope wave functions in terms of harmonic-oscillator wave functions, as functions of the in-plane magnetic field, cyclotron orbit-center position, and quantum-well widths. This procedure allows us to consider the different terms in the Hamiltonian on equal footing, avoiding therefore the use of approximate methods to obtain the envelope wave functions and the corresponding energy spectrum. Results obtained for the Land\'e ${g}_{\ensuremath{\perp}}$-factor were found in quite good agreement with available experimental measurements.

Effect of in-plane magnetic field on the spin Hall effect in a Rashba-Dresselhaus system

In a two-dimensional electron gas with Rashba and Dresselhaus spin-orbit couplings, there are two spin-split energy surfaces connected with a degenerate point. Both the energy surfaces and the topology of the Fermi surfaces can be varied by an in-plane magnetic field. We find that, if the chemical potential falls between the bottom of the upper band and the degenerate point, then simply by changing the direction of the magnetic field, the magnitude of the spin Hall conductivity can be varied by about 100 percent. Once the chemical potential is above the degenerate point, the spin Hall conductivity becomes the constant $e/8\pi$, independent of the magnitude and direction of the magnetic field. In addition, we find that the in-plane magnetic field exerts no influence on the charge Hall conductivity.

Transverse negative magnetoresistance of two-dimensional structures in the presence of a strong in-plane magnetic field: Weak localization as a probe of interface roughness

The interference induced transverse negative magnetoresistance of GaAs/InGaAs/GaAs quantum well heterostructures has been studied in the presence of strong in-plane magnetic field. It is shown that effect of in-plane magnetic field is determined by the interface roughness and strongly depends on the relationship between mean free path, phase breaking length and roughness correlation length. Analysis of the experimental results allows us to estimate parameters of short- and long-range correlated roughness which have been found in a good agreement with atomic force microscopy data obtained for just the same samples.

Resonant magneto-tunneling through shallow impurity states in double barrier heterostructures

A theoretical study is presented of the effects of in-plane magnetic fields on the I–V characteristic curves associated with resonant electron tunneling through shallow impurity states in GaAs/(Al,Ga)As double-barrier heterostructures. A simple one-band tight-binding Hamiltonian is used and the current is obtained by adopting Keldysh diagrammatic techniques for nonequilibrium processes. As the field strength increases the peak associated with the donor-assisted tunneling shifts to lower voltages whereas the resonance associated with tunneling through the first subband shifts to higher ones. Also, the intensities are both reduced, in qualitatively good agreement with the experimental reports of Sakai et al. [Phys. Rev. B. 48, 5664 (1993)].

Orbital effects of in-plane magnetic fields probed by mesoscopic conductance fluctuations

We use the high sensitivity to magnetic flux of mesoscopic conductance fluctuations in large quantum dots to investigate changes in the two-dimensional electron dispersion caused by an in-plane magnetic field. In particular, changes in effective mass and the breaking of momentum reversal symmetry in the electron dispersion are extracted quantitatively from correlations of conductance fluctuations. New theory is presented, and good agreement between theory and experiment is found.

Effects of in-plane magnetic fields on spin transitions in bilayer quantum Hall states

In a bilayer system, various phase transitions occur due to the competition among the cyclotron, Zeeman and tunneling energies. We investigate effects of an in-plane magnetic field B ||, which couples subband and Landau levels with the same spin and modulate wave functions extended to both layers, on transitions of quantum Hall states in such a system. As B || is applied, we observe that crossings between opposite spin levels as well as those between the same spin levels disappear in characteristic sequences. While anticrossings of single-particle levels are sufficient to explain the observed behavior for crossings at ν=4, the data at ν=6 are not understood in a single-particle picture, and suggest Coulomb-induced mixing of different spin levels.

Electronic structure of diluted magnetic semiconductor superlattices: In-plane magnetic field effect

The electronic structure of diluted magnetic semiconductor (DMS) superlattices under an in-plane magnetic field is studied within the framework of the effective-mass theory; the strain effect is also included in the calculation. The numerical results show that an increase of the in-plane magnetic field renders the DMS superlattice from the direct band-gap system to the indirect band-gap system, and spatially separates the electron and the hole by changing the type-I band alignment to a type-II band alignment. The optical transition probability changes from type I to type II and back to type I like at large magnetic field. This phenomenon arises from the interplay among the superlattice potential profile, the external magnetic field, and the $\mathrm{sp}\ensuremath{-}d$ exchange interaction between the carriers and the magnetic ions. The shear strain induces a strong coupling of the light- and heavy-hole states and a transition of the hole ground states from ``light''-hole to ``heavy''-hole-like states.

Effect of in-plane magnetic field on cyclotron resonance in various types of 2DES

The in-plane magnetic field ( B ||) dependence of cyclotron resonance is investigated in both single and double layer two-dimensional electron systems by Fourier spectrometry in tilted magnetic fields. The observed B || dependence of the cyclotron mass ( m C) is complicated and varies with perpendicular magnetic field in the double layer system. The splitting of m C by B || around filling factor 2 is observed in the single layer system.

Effect of an in-plane magnetic field on magnetic phase transitions inν=2bilayer quantum Hall systems

By using the effective bosonic spin theory, which is recently proposed by Demler and Das Sarma [ Phys. Rev. Lett. 82, 3895 (1999) ], we analyze the effect of an external in-plane magnetic field on the magnetic phase transitions of the bilayer quantum Hall system at filling factor nu=2. It is found that the quantum phase diagram is modified by the in-plane magnetic field. Therefore, quantum phase transitions can be induced simply by tilting the magnetic field. The general behavior of the critical tilted angle for different layer separations and interlayer tunneling amplitudes is shown. We find that the critical tilted angles being calculated agree very well with the reported values. Moreover, a universal critical exponent for the transition from the canted antiferromagnetic phase to the ferromagnetic phase is found to be equal to 1/2 within the present effective theory.

In-plane magnetic-field effect on transport properties of the chiral edge state in a quasi-three-dimensional quantum well structure

The transport properties of a quasi-three-dimensional, 200-layer quantum-well structure are investigated at integer filling in the quantum Hall state, concomitant with the chiral edge state condition. We find that the transverse magnetoresistance ${R}_{\mathrm{xx}},$ the Hall resistance ${R}_{\mathrm{xy}},$ and the vertical resistance ${R}_{\mathrm{zz}}$ all follow a similar behavior with both temperature and in-plane magnetic field. A general characteristic of the influence of increasing in-plane field ${B}_{\mathrm{in}}$ is that the quantization condition first improves, but above a critical value ${B}_{\mathrm{in}}^{C},$ the quantization is systematically removed. We consider the interplay of the chiral edge state transport and the bulk (quantum Hall) transport properties. This mechanism may arise from the competition of the cyclotron energy with the superlattice band-structure energies. A comparison of the results with existing theories of the chiral edge state transport with in-plane field is also discussed.

Destabilizing Effect of In-Plane Magnetic Field on Panel Flutter

ABSTRACTDestabilizing effect of magnetic damping on the supersonic panel flutter is investigated. The linear piston theory is available to formulate the air force at high Mach numbers. A plate in supersonic flow can be stabilized by reducing the compression force perpendicular to the flow. However, once the dynamic pressure parameter exceeds some critical value, the time rate of motion becomes complex then the flutter occurs. In this paper, the strength of in-plane magnetic field to reduce the panel flutter under higher dynamic pressure parameter is determined. Due to the complexity in finding the exact solution of plate motion, Galerkin solution with different terms of truncation is adopted herein. Therefore, the exact solution can be obtained by using the four-term solution as an initial value. The most attractive feature is that the supersonic flutter can be avoided efficiently through the application of in-plane magnetic field.

Magnetotunneling in interband tunnel structures

We examine the effect of in-plane magnetic fields on transport properties of InAs/GaSb/AlSb-based resonant interband tunneling (RIT) structures and barrierless resonant interband tunneling structures using the multiband k\ensuremath{\cdot}p quantum transmitting boundary method [Y. X. Liu et al., Phys. Rev. B 54, 5765 (1996)]. In interband tunnel structures with GaSb quantum wells, the primary peak found in the current-voltage characteristic is due to the coupling of InAs conduction-band electrons to quantized GaSb light-hole states, and a weaker shoulder peak typically shows up as the result of coupling to quantized GaSb heavy-hole states. We find that in-plane magnetic fields can enhance this electron-heavy-hole coupling, resulting in a more pronounced shoulder peak in the current-voltage characteristic. Qualitative agreement between our calculations and experimental data on RIT structures offers strong evidence for hole-mixing induced electron-heavy-hole coupling in interband tunnel structures.

Resonant tunneling of electrons via 20 nm scale InAs quantum dot and magnetotunneling spectroscopy of its electronic states

The resonant tunneling of electrons through a 20 nm scale InAs quantum dot bound by a pair of very thin AlAs barriers is studied. A well-resolved composite peak resulting from the ground 1s states was observed at 4.2 K in current–voltage characteristics. By investigating the effects of inplane magnetic fields, the shape of the wave function and the spatial extent of the first two electronic states are clarified.

Magneto-optical absorption spectra and self-similarity of GaAs–(Ga,Al)As quasiperiodic Fibonacci superlattices under in-plane magnetic fields

A theoretical study of the effects of in-plane magnetic fields on the interband optical absorption spectra of quasiperiodic GaAs–(Ga,Al)As Fibonacci superlattices is presented within the effective-mass approximation. The electron-envelope wave functions and magnetic subbands are obtained by an expansion in harmonic-oscillator wave functions. The theoretical optical absorption spectra are calculated for magnetic fields related by integer powers of the golden mean τ=(1+√5)/2. It is unambiguously shown that, for magnetic-field values scaled by τ2n, the corresponding optical absorption spectra essentially exhibit a self-similar behavior, with the width of the peaks increasing linearly with the field, in agreement with the experimental results by D. Toet, M. Potemski, Y. Y. Wang, J. C. Maan, L. Tapter, and K. Ploog [Phys. Rev. Lett. 66, 2128 (1991)].