scholarly journals Effects of a Perpendicularly Applied Magnetic Field on Harmonically Driven Quasi-two-dimensional Electron Gas: the Static Macrostates Symmetry Breaking and Generation of Even Harmonics in System Output

2021 ◽  
Vol 17 (2) ◽  
pp. 141-156
Author(s):  
V. A. Smolar ◽  
◽  
T. I. Karyakina ◽  
I. I. Maglevanny ◽  
◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Internal Control ◽  
Order Parameter ◽  
High Harmonic ◽  
Two Dimensional ◽  
Control Parameters ◽  
Nonmonotonic Dependence ◽  
Cooperative Effects ◽  
Even Harmonics

In this paper, we consider activation processes in a nonlinear metastable system based on a quasi-two-dimensional superlattice and study the dynamics of such a system, which is externally driven by a harmonic force in regimes of controlled instabilities. The spontaneous transverse electric field is considered as an order parameter and the forced violations of the order parameter are considered as a response of a system to periodic driving. The internal control parameters are the longitudinal applied electric field, the sample temperature and the magnetic field which is orthogonal to the superlattice plane. We investigate the cooperative effects of self-organization and high harmonic forcing in such a system from the viewpoint of catastrophe theory It is shown through numerical simulations that the additional magnetic field breaks the static macrostates symmetry and leads to generation of even harmonics; it also allows the control of the intensity of particular harmonics. The intensity of even harmonics demonstrates resonant-type nonmonotonic dependence on control parameters with the maxima at points close to critical points of the synergetic potential.

RESONANT SPIN POLARIZATION IN A TWO-DIMENSIONAL HOLE GAS

2011 ◽  
Vol 25 (15) ◽  
pp. 1259-1270
Author(s):  
TIANXING MA
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Spin Polarization ◽  
Zeeman Splitting ◽  
Resonant Peak ◽  
Two Dimensional ◽  
Structural Inversion ◽  
Inversion Asymmetry ◽  
Peak Increase ◽  
Luttinger Hamiltonian

Within the Luttinger Hamiltonian, electric-field-induced resonant spin polarization of a two-dimensional hole gas in a perpendicular magnetic field was studied. The spin polarization arising from splitting between the light and the heavy hole bands shows a resonant peak at a certain magnetic field. Especially, the competition between the Luttinger term and the structural inversion asymmetry leads to a rich resonant peaks structure, and the required magnetic field for the resonance may be effectively reduced by enlarging the effective width of the quantum well. Furthermore, the Zeeman splitting tends to move the resonant spin polarization to a relative high magnetic field and destroy these rich resonant spin phenomena. Finally, both the height and the weight of the resonant peak increase as the temperature decreases. It is believed that such resonant spin phenomena may be verified in the sample of a two-dimensional hole gas, and it may provide an efficient way to control spin polarization by an external electric field.

scholarly journals Nematic topological defects positionally controlled by geometry and external fields

2018 ◽  
Vol 9 ◽  
pp. 109-118 ◽  
Author(s):  
Pavlo Kurioz ◽  
Marko Kralj ◽  
Bryce S Murray ◽  
Charles Rosenblatt ◽  
Samo Kralj
Keyword(s):  
Electric Field ◽  
Topological Charge ◽  
Order Parameter ◽  
Topological Defects ◽  
Two Dimensional ◽  
External Fields ◽  
Nematic Ordering ◽  
Spatial Positioning ◽  
A Charge ◽  
The Impact

Using a Landau–de Gennes approach, we study the impact of confinement topology, geometry and external fields on the spatial positioning of nematic topological defects (TDs). In quasi two-dimensional systems we demonstrate that a confinement-enforced total topological charge of m > 1/2 decays into elementary TDs bearing a charge of m = 1/2. These assemble close to the bounding substrate to enable essentially bulk-like uniform nematic ordering in the central part of a system. This effect is reminiscent of the Faraday cavity phenomenon in electrostatics. We observe that in certain confinement geometries, varying the correlation length size of the order parameter could trigger a global rotation of an assembly of TDs. Finally, we show that an external electric field could be used to drag the boojum fingertip towards the interior of the confinement cell. Assemblies of TDs could be exploited as traps for appropriate nanoparticles, opening several opportunities for the development of functional nanodevices.

Magnetometric resistivity (MMR) anomalies of two‐dimensional structures

Geophysics ◽  
1979 ◽  
Vol 44 (5) ◽  
pp. 947-958 ◽  
Author(s):  
E. Gomez Trevino ◽  
R. N. Edwards
Keyword(s):  
Magnetic Field ◽  
Integral Equation ◽  
Fourier Transform ◽  
Electric Field ◽  
Current Source ◽  
Two Dimensional ◽  
Galvanic Current ◽  
One Dimensional ◽  
The Magnetic Field ◽  
Surface Integrals

An inexpensive, rapid method has been developed for computing all three components of the magnetic field due to galvanic current flow from a point electrode in the vicinity of a conductive subsurface structure of infinite strike‐length and arbitrary cross‐section. For any three‐dimensional (3-D) structure, the magnetic field may be written as a sum of surface integrals over boundaries defining changes in conductivity by a direct modification of the Biot‐Savart law. The integrand of each surface integral includes the components of the electric field tangential to the boundary, which may be evaluated on the boundary using a standard integral equation technique. In the case of a two‐dimensional (2-D) structure, a reformulation of the theory by taking a one‐dimensional Fourier transform along the strike results in the reduction of both the surface integrals necessary to solve the integral equation for the electric field, and the integrals used in computing the magnetic field, to line integrals in wavenumber domain. We evaluate the integrals numerically and solve the integral equation for each of about ten wavenumbers; finally, we obtain the magnetic field in space domain through a concluding one‐dimensional inverse Fourier transform. Type curves and characteristic curves for the simple model of a buried horizontal cylinder beneath a thin layer of conductive overburden are constructed. In the absence of overburden, the half‐width of the anomaly is linearly related to the depth of the cylinder. In the presence of overburden, the form of the anomaly may be predicted in a simple manner from the corresponding anomaly in the absence of overburden, provided the distance from the current source is sufficiently large for most of the available current to have penetrated the overburden.

A Shubnikov-De Haas Study of Tilted Magnetic Field in the HgTe/CdTe Superlattice

1994 ◽  
Vol 299 ◽  
Author(s):  
Ikai Lo ◽  
W. C. Mitchel ◽  
D. Boeringer ◽  
K.A. Harris ◽  
R.W. Yanka ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Temperature Dependence ◽  
Electrostatic Field ◽  
Electron Gas ◽  
Two Dimensional ◽  
Dimensional Electron ◽  
Two Dimensional Electron Gas ◽  
Dimensional Electron Gas ◽  
Tilted Magnetic Field

AbstractWe have measured the Shubnikov-de Haas (SdH) effect in a HgTe/CdTe superlattice (SL) with a tilted magnetic field in the absence of an external electric field. We found that the peaks of the SdH oscillation changed with Bcosθ, indicating the two-dimensional character of the electron gas. The carrier concentration of the two-dimensional electron gas (2DEG) is equal to 2.95×1011 cm−2. The 2DEG shows the existence of a Stark ladder, which is caused by the internal electrostatic field, near the interface between the substrate and the SL. From the temperature dependence of the SdH measurements, we also show that the 3DEG in the SL miniband contributes to the non-oscillatory magnetoresistance and that the mobility of 3DEG in the miniband is lower than that of 2DEG in the Stark ladder.

scholarly journals Effect of a dc electric field on the longitudinal resistance of two-dimensional electrons in a magnetic field

2007 ◽  
Vol 75 (8) ◽  
Author(s):  
Jing-qiao Zhang ◽  
Sergey Vitkalov ◽  
A. A. Bykov ◽  
A. K. Kalagin ◽  
A. K. Bakarov
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Two Dimensional ◽  
Dc Electric Field ◽  
Longitudinal Resistance

scholarly journals Isospin magnetism and spin-polarized superconductivity in Bernal bilayer graphene

Science ◽  
2022 ◽  
Author(s):  
Haoxin Zhou ◽  
Ludwig Holleis ◽  
Yu Saito ◽  
Liam Cohen ◽  
William Huynh ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Order Parameter ◽  
Degrees Of Freedom ◽  
Bilayer Graphene ◽  
Zero Magnetic Field ◽  
Cooper Pairing ◽  
Two Dimensional ◽  
Van Hove Singularity ◽  
Spin Polarized ◽  
Spin Triplet

In conventional superconductors, Cooper pairing occurs between electrons of opposite spin. We observe spin-polarized superconductivity in Bernal bilayer graphene when doped to a saddle-point van Hove singularity generated by large applied perpendicular electric field. We observe a cascade of electrostatic gate-tuned transitions between electronic phases distinguished by their polarization within the isospin space defined by the combination of the spin and momentum-space valley degrees of freedom. Although all of these phases are metallic at zero magnetic field, we observe a transition to a superconducting state at finite B ‖ ≈ 150mT applied parallel to the two-dimensional sheet. Superconductivity occurs near a symmetry breaking transition, and exists exclusively above the B ‖ -limit expected of a paramagnetic superconductor with the observed transition temperature T C ≈ 30mK, consistent with a spin-triplet order parameter.

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