Quantizing Magnetic Field Research Articles

Radio Emission of Pulsars. II. Coherence Catalyzed by Cerenkov-unstable Shear Alfvén Waves

This paper explores small-scale departures from force-free electrodynamics around a rotating neutron star, extending our treatment of resistive instability in a quantizing magnetic field. A secondary, Cerenkov instability is identified: relativistic particles flowing through thin current sheets excite propagating charge perturbations that are localized near the sheets. Growth is rapid at wavenumbers below the inverse ambient skin depth k p,ex. Small-scale Alfvénic wavepackets are promising sources of coherent curvature radiation. When the group Lorentz factor , where R c is the magnetic curvature radius, a fraction ∼10−3–10−2 of the particle kinetic energy is radiated into the extraordinary mode at a peak frequency ∼10−2 ck p,ex. Consistency with observations requires a high pair multiplicity (∼103–5) in the pulsar magnetosphere. Neither the primary, slow resistive instability nor the secondary, Alfvénic instability depend directly on the presence of magnetospheric gaps, and may activate where the mean current is fully supplied by outward drift of the corotation charge. The resistive mode is overstable and grows at a rate comparable to the stellar spin frequency; the model directly accommodates strong pulse-to-pulse radio flux variations and coordinated subpulse drift. Alfvén mode growth can track the local plasma conditions, allowing for lower-frequency emission from the outer magnetosphere. Beamed radio emission from charged packets with γ gr ∼ 50–100 also varies on submillisecond timescales. The modes identified here will be excited inside the magnetosphere of a magnetar, and may mediate Taylor relaxation of the magnetic twist.

Radio Emission of Pulsars. I. Slow Tearing of a Quantizing Magnetic Field

The pulsed radio emission of rotating neutron stars is connected to slow tearing instabilities feeding off an inhomogeneous twist profile within the open circuit. This paper considers the stability of a weakly sheared, quantizing magnetic field in which the current is supported by a relativistic particle flow. The electromagnetic field is almost perfectly force free, and particles are confined to the lowest Landau state, experiencing no appreciable curvature drift. In a charge-neutral plasma, we find multiple branches of slowly growing tearing modes, relativistic analogs of the double-tearing mode, with peak growth rate . Here, B z is the strong (nearly potential) guide magnetic field, J z the field-aligned current density, and is the mode wavenumber normalized by the current gradient scale. These modes are overstable when the plasma carries a net charge, with the real frequency proportional to the imbalance in the densities of positive and negative charges. An isolated current sheet thinner than the skin depth supports localized tearing modes with growth rate scaling as (sheet thickness/skin depth)−1/2. In a pulsar, the peak growth rate is comparable to the angular frequency of rotation, , slow compared with the longitudinal oscillations of particles and fields in a polar gap. The tearing modes experience azimuthal drift reminiscent of subpulse drift and are a promising driver of pulse-to-pulse flux variations. A companion paper demonstrates a Cerenkov-like instability of current-carrying Alfvén waves in thin current sheets with relativistic particle flow and proposes coherent curvature emission by these waves as a source of pulsar radio emission.

Excitation of weak and strong guided waves in a semiconductor slab and their strong coupling with confined magnetoexcitons

We have obtained and analyzed optical spectra of a semiconductor slab, containing a quantum well which serves as a source of magnetoexcitons in the presence of an external dc magnetic field. Our setup corresponds to the optical technique based on the breaking of the total internal reflection. Specifically, the semiconductor slab is sandwiched between two external leads/prisms separated from the slab by two gap layers of a dielectric or metal. The reflectivity, transmissivity, and absorption spectra for such a system in a quantizing magnetic field were revealed to display a resonant structure originating from the excitation of electromagnetic modes localized on the semiconductor slab which are strongly coupled with the confined magnetoexcitons. It is surprising that the Rabi splitting for the setup with dielectric gap layers (weak guiding) turns out to be greater than that for metallic and even semiconductor microcavities (strong guiding). Our results were verified by comparing the calculated optical spectra with the dispersion curves for localized modes derived analytically.

Phonon-drag thermopower and thermoelectric performance of MoS2 monolayer in quantizing magnetic field

We present a theory of phonon-drag thermopower, , in MoS2 monolayer at a low-temperature regime in the presence of a quantizing magnetic field B. Our calculations for consider the electron–acoustic phonon interaction via deformation potential (DP) and piezoelectric (PE) couplings for longitudinal (LA) and transverse (TA) phonon modes. The unscreened TA-DP is found to dominate over other mechanisms. The is found to oscillate with the magnetic field where the lifting effect of the valley and spin degeneracies in MoS2 monolayer has been clearly observed. An enhanced with a peak value of mV K−1 at about T = 10 K is predicted, which is closer to the zero field experimental observation. In the Bloch–Grüneisen regime the temperature dependence of gives the power-law , where δ e varies marginally around 3 and 5 for unscreened and screened couplings, respectively. In addition, is smaller for larger electron density n e . The power factor PF is found to increase with temperature T, decrease with n e , and oscillate with B. The prediction of an increase of thermal conductivity with temperature and the magnetic field is responsible for the limit of the figure of merit (ZT). At a particular magnetic field and temperature, ZT can be maximized by optimizing electron density. By fixing cm−2, the highest ZT is found to be 0.57 at T = 5.8 K and B = 12.1 T. Our findings are compared with those in graphene and MoS2 for the zero-magnetic field.

Electrophysical properties of compensated n-Germanium

Measurements of the transverse magnetoresistance and the Hall effect of compensated n-Ge crystals in the weak and strong magnetic fields at liquid nitrogen temperature have been carried out. It was revealed that in crystals with a sufficiently high degree of compensation, the space charge regions play a significant role in the scattering of charge carriers, which cause an increase in the transverse magnetoresistance (with increasing H) and its linear dependence on H in the region of strong magnetic fields. It was shown that in sufficiently strongly compensated crystals, the scattering of current carriers by the space charge regions is practically isotropic. It was found that thermal annealing (350 °C; 60 h) of compensated oxygen-containing n-Ge, which significantly reduces the compensation degree due to the arising donor-type oxygen complexes, leads to a decrease in the slope of the field dependences of the transverse magnetoresistance in the quantizing magnetic fields.

Electron power loss in metal-oxide nanostructures in quantizing magnetic field

Hot-electron power loss via electron interaction with bulk longitudinal polar optical phonon in metal-oxide two dimensional nanostructures in the presence of zero and finite quantizing magnetic fields is investigated using electron temperature model. The dependence of power loss in two-dimensional nanostructures of transparent conducting oxides like ZnO, SnO2, CdO, In2O3, Ga2O3 is presented as a function of electron temperature and carrier density in zero and finite magnetic fields. Numerical calculations establish that external quantizing magnetic field enhances power loss of electrons. Further, electron power loss is proportional to the electron temperature and varies inversely with the carrier density. The electron magneto-power loss qualitatively differs from the oscillating dependence of the electron-phonon scattering on the quantizing magnetic field.

Influence of a quantizing magnetic field on the Fermi energy oscillations in two-dimensional semiconductors

In this article we investigated the effects of quantizing magnetic field and temperature on Fermi energy oscillations in nanoscale semiconductor materials. It is shown that the Fermi energy of a nanoscale semiconductor material in a quantized magnetic field is quantized. The distribution of the Fermi-Dirac function is calculated in low-dimensional semiconductors at weak magnetic fields and high temperatures. The proposed theory explains the experimental results in two-dimensional semiconductor structures with a parabolic dispersion law.

Propagation of longitudinal acoustic phonons in ZrTe5 exposed to a quantizing magnetic field

The compound ${\mathrm{ZrTe}}_{5}$ has recently been connected to a charge-density-wave (CDW) state with intriguing transport properties. Here, we investigate quantum oscillations in ultrasound measurements that microscopically originate from electron-phonon coupling and analyze how these would be affected by the presence or absence of a CDW. We calculate the phonon self-energy due to electron-phonon coupling, and from there deduce the sound-velocity renormalization and sound attenuation. We find that the theoretical predictions for a metallic Dirac model resemble the experimental data on a quantitative level for magnetic fields up to the quantum-limit regime.

The Magneto Electron Statistics in Heavily Doped N Type-Intrinsic-P Type-Intrinsic Structures.

In this paper we study the Electron Statistics in Heavily Doped N Type-Intrinsic-P Type-Intrinsic structures of non-linear optical, tetragonal and opto-electronic materials in the presence of magnetic quantization. It is found taking such heavily doped structures of Cd₃As₂, CdGeAs₂, InAs, InSb, Hg1-xCdxTe, In1-xGaxAsyP1-y as examples that the Fermi energy (EF) oscillates with inverse quantizing magnetic field (1/B) and increases with increasing electron concentration with different numerical magnitudes which is the signature of respective band structure. The numerical value of the Fermi energy is different in different cases due to the different values of the energy band constants.

Pseudoscalar U(1) spin liquids in α−RuCl3

A recent experiment has reported oscillations of the thermal conductivity of $\alpha$-RuCl$_3$ driven by an in-plane magnetic field that are reminiscent of the quantum oscillations in metals. At first glance, these observations are consistent with the presence of the long-sought-after spinon Fermi surface state. Strikingly, however, the experiment also reported vanishing thermal Hall conductivity coexisting with the oscillations of the longitudinal one. Such absence of the thermal Hall effect must originate from crystalline symmetries of $\alpha$-RuCl$_3$. But if the system was a traditional spinon fermi surface state, these symmetries would also necessarily prohibit the emergence of a magnetic field acting on the spinons, in stark contradiction with the presence of quantum oscillations in experiments. To reconcile these observations, we introduce a new class of symmetry enriched ``pseudoscalar" U(1) spin liquids in which certain crystalline symmetries act as a particle-hole conjugation on the spinons. The associated pseudoscalar spinon Fermi surface states allow for the coexistence of an emergent Landau quantizing magnetic field while having an exactly zero thermal Hall conductivity. We develop a general theory of these states by constructing Gutzwiller-projected wave-functions and describing how they naturally appear as U(1) spin liquids with a distinctive projective symmetry group implementation of crystalline symmetries in the fermionic parton representation of spins. We propose that the field induced quantum disordered state in $\alpha$-RuCl$_3$ descends from a pseudoscalar spinon fermi surface state that features compensated spinon-particle and spinon-hole pockets possibly located around the $M$ points of its honeycomb Brillouin zone. These points are connected via a wave-vector associated with the emergence of the competing zig-zag antiferromagnetic state.

Laughlin anyon complexes with Bose properties

Two-dimensional electron systems in a quantizing magnetic field are regarded as of exceptional interest, considering the possible role of anyons—quasiparticles with non-boson and non-fermion statistics—in applied physics. To this day, essentially none but the fractional states of the quantum Hall effect (FQHE) have been experimentally realized as a system with anyonic statistics. In determining the thermodynamic properties of anyon matter, it is crucial to gain insight into the physics of its neutral excitations. We form a macroscopic quasi-equilibrium ensemble of neutral excitations - spin one anyon complexes in the Laughlin state ν = 1/3, experimentally, where ν is the electron filling factor. The ensemble is found to have such a long lifetime that it can be considered the new state of anyon matter. The properties of this state are investigated by optical techniques to reveal its Bose properties.

Propagation and energy of bright and dark solitons in magnetized quantum semiconductor plasmas in the presence of Bohm potential effect

A theoretical investigation is presented for the bright and dark solitons in GaAs, GaSb, InP, and GaN quantum magnetized semiconductor plasma systems. The plasma system consists of electrons, holes, and ions, all existed in a quantizing magnetic field. The Zakharov–Kuznetsov (ZK) equation is derived by using the reductive perturbation method. The bright and the dark soliton solutions are derived for the ZK equation. The electric field and the soliton energy were also derived. The present results are considered to be beneficial in understanding the waves propagating in quantum semiconductor plasmas on an ultrafast time scale in semiconductors nanostructures that are applicable for quantum computing.

Ion Acoustic Shocks in a Weakly Relativistic Ion-Beam Degenerate Magnetoplasma

A theoretical investigation is carried out to study the propagation properties of ion acoustic shocks in a plasma comprising of positive inertial ions, weakly relativistic ion beam and trapped electrons in the presence of a quantizing magnetic field. By using the reductive perturbation technique, the Korteweg–de Vries-Burgers (KdVB) equation and oscillatory shocks solution are derived. The characteristics of such kinds of shock waves are examined and discussed in detail under suitable conditions for different physical parameters. The strength of the magnetic field, ion beam concentration and ion-beam streaming velocity have a great influence on the amplitude and width of the shock waves and oscillatory shocks. The results may be useful to study the characteristics of ion acoustic shock waves in dense astrophysical regions such as neutron stars.

INFLUENCE О F А STR О NG M А GNETIC FIELD О N FERMI ENERGY О SCILL А TI О NS IN TW О -DIMENSI О N А L SEMIC О NDUCT О R M А TERI А LS

This article shows that the Fermi levels of a nanoscale semiconductor in a quantizing magnetic field are quantized. A method is proposed for calculating the Fermi energy oscillations for a two-dimensional electron gas at different magnetic fields and temperatures. An analytical expression is obtained for calculating the Fermi-Dira c distribution function at high temperatures and weak magnetic fields. With the help of the propos ed formula, the experimental results in nanoscale semiconductor structures are investigated. Using fo rmula, Fermi energy oscillations are explained for two-dimensional electron gases in quantum wells (quantum wells, mainly GaAs/GaAlAs heterostructures) with a parabolic dispersion law. Keywоrds:quаntizing mа gnetic field, temperаture, Fermi energy, n аnоscаle semicоnductоrs,twо-dimensiоnаl structures, dispersiоn.

ВЫЧИСЛЕНИЕ ТЕМПЕРАТУРНОЙ ЗАВИСИМОСТИ ЭНЕРГЕТИЧЕСКОГО СПЕКТРА НОСИТЕЛЕЙ ЗАРЯДОВ В ПОЛУПРОВОДНИКАХ ПРИ ВОЗДЕЙСТВИИ СИЛЬНОГО МАГНИТНОГО ПОЛЯ

The energy spectrum of free holes in a st rong magnetic field is calculated for a non- quadratic dispersion law. The temperature dependen ce of the broadening of the Landau levels of holes in crystals with the Kane dispersion law has been studied. A new method for calculating the discrete energy spectrum in a quantizing magnetic field is proposed

EFFECTS OF TEMPERATURE AND A TRANSVERSAL QUANTIZING MAGNETIC FIELD ON THE FORBIDDEN BAND OF A QUANTUM WELL

This article considers the temperature dependence of the band gap in quantum-well heterostructures in the presence of a transverse quantizing magnetic field. An analytical expression is obtained for determining the band gap of a rect angular quantum well at various magnetic fields and temperatures. The proposed formulas well exp lain the experimental results obtained for quantum-well semiconductor structures

The kinectics of energy relaxation in quantum wells in a quantizing magnetic field

The kinetics of the intraband relaxation of the electron energy in the system of Landau levels lying below the the optical phonon energy is studied. Unusual behaviour of the relaxation of electronic subsystem is found. Even though its main channel is the emission of optical phonons, the total relaxation time is several orders of magnitude higher than the characteristic scattering times on optical phonons.

Effect of the Landau quantization of electrons on the inner crusts of hot neutron stars

In the present work we study the effects of strongly quantizing magnetic fields and finite temperature on the properties of inner crusts of hot neutron stars. The inner crust of a neutron star contains neutron-rich nuclei arranged in a lattice and embedded in gases of free neutrons and electrons. We describe the system within the Wigner-Seitz (WS) cell approximation. The nuclear energy is calculated using Skyrme model with SkM* interaction. To isolate the properties of nuclei we follow the subtraction procedure presented by Bonche, Levit and Vautherin, within the Thomas-Fermi approximation. We obtain the equilibrium properties of inner crust for various density, temperatures and magnetic fields by minimizing the free energy of the WS cell satisfying the charge neutrality and $\beta-$equilibrium conditions. We infer that at a fixed baryon density and temperature, strong quantizing magnetic field reduces the cell radii, neutron and proton numbers in the cell compared with the field free case. However, the nucleon number in the nucleus increases in presence of magnetic field. The free energy per nucleon also decreases in magnetized inner crust. On the other hand, we find that finite temperature tends to smear out the effects of magnetic field. Our results can be important in the context of $r-$process nucleosynthesis in the binary neutron star mergers.

Calculation of the Fermi–Dirac Function Distribution in Two-Dimensional Semiconductor Materials at High Temperatures and Weak Magnetic Fields

This article investigated the effects of a quantizing magnetic field and temperature on Fermi energy oscillations in nanoscale semiconductor materials. It is shown that the Fermi energy of a nanoscale semiconductor material in a quantizing magnetic field is quantized. The distribution of the Fermi–Dirac function is calculated in low-dimensional semiconductors at weak magnetic fields and high temperatures. The proposed theory explains the experimental results in two-dimensional semiconductor structures with a parabolic dispersion law.

Out-of-Plane Dielectric Susceptibility of Graphene in Twistronic and Bernal Bilayers.

We describe how the out-of-plane dielectric polarizability of monolayer graphene influences the electrostatics of bilayer graphene—both Bernal (BLG) and twisted (tBLG). We compare the polarizability value computed using density functional theory with the output from previously published experimental data on the electrostatically controlled interlayer asymmetry potential in BLG and data on the on-layer density distribution in tBLG. We show that monolayers in tBLG are described well by polarizability αexp = 10.8 Å3 and effective out-of-plane dielectric susceptibility ϵz = 2.5, including their on-layer electron density distribution at zero magnetic field and the interlayer Landau level pinning at quantizing magnetic fields.