External Static Magnetic Field Research Articles

Hinge modes and surface states in second-order topological three-dimensional quantum Hall systems induced by charge density modulation

We consider a system of weakly coupled one-dimensional wires forming a three-dimensional stack in the presence of a spatially periodic modulation of the chemical potential along the wires, equivalent to a charge density wave (CDW). An external static magnetic field is applied parallel to the wire axes. We show that, for a certain parameter regime, due to interplay between the CDW and magnetic field, the system can support a second-order topological phase characterized by the presence of chiral quasi-1D Quantum Hall Effect (QHE) hinge modes. Interestingly, we demonstrate that direction of propagation of the hinge modes depends on the phase of the CDW and can be reversed only by electrical means without the need of changing the orientation of the magnetic field. Furthermore, we show that the system can also support 2D chiral surface QHE states, which can coexist with one-dimensional hinge modes, realizing a scenario of a hybrid high-order topology. We show that the hinge modes are robust against static disorder.

Enhancement of electron density in the interaction of high‐power electromagnetic waves with inhomogeneous magnetized plasma

AbstractPropagation characteristics of a high‐power electromagnetic wave through an inhomogeneous magnetized plasma is investigated. Considering the momentum transfer equations for electrons and ions and taking into account the ponderomotive force, the distribution of electron density and dielectric permittivity are obtained. Using non‐linear dielectric permittivity and Maxwell's equations in the absence of external current and charge densities, non‐linear wave equations are achieved. The results indicate that the external static magnetic field can modify the profiles of both the electric and magnetic fields. It is also shown that the external static magnetic field enhances the amplitude of the electron density and the non‐linear dielectric permittivity.

Light storage and retrieval in spherical semiconductor quantum dots with on-center hydrogen impurity in magnetic field

We investigate the light propagation through the medium consisted of spherical semiconductor quantum dots with an on-center hydrogen impurity under the regime of the electromagnetically induced transparency. The weak probe and strong control laser couple to the medium, forming the three-level ladder-type coupling scheme. Maxwell-Bloch equations are solved numerically and analytically to obtain the spatial and temporal dependence of the probe pulse envelope. We observed that the probe pulse can be stored to and retrieved from the medium, with storage times of the order of nanoseconds being obtained. The external static magnetic field is shown to affect the energy level structure of the hydrogen impurity, reshaping the output probe pulse. We demonstrated that exposing the medium to cryogenic temperatures significantly increases the storage efficiency and storage time. These phenomena can greatly contribute to quantum information processing , leading to the construction of optical buffers, optical switches and quantum memories. • Slow light with the group velocity reduced by a factor 15 is achieved. • Storage times of the order of nanoseconds at room temperatures are obtained. • Approximate analytic results accurately describe the storage efficiency. • External magnetic field reshapes the output pulse and acts as an optical switch. • At cryogenic temperatures, storage times are increased to hundreds of nanoseconds.

Adsorption transition of a grafted ferromagnetic filament controlled by external magnetic fields.

Extensive Langevin dynamics simulations are used to characterize the adsorption transition of a flexible magnetic filament grafted onto an attractive planar surface. Our results identify different structural transitions at different ratios of the thermal energy to the surface attraction strength: filament straightening, adsorption, and the magnetic flux closure. The adsorption temperature of a magnetic filament is found to be higher in comparison to an equivalent nonmagnetic chain. The adsorption has been also investigated under the application of a static homogeneous external magnetic field. We found that the strength and the orientation of the field can be used to control the adsorption process, providing a precise switching mechanism. Interestingly, we have observed that the characteristic field strength and tilt angle at the adsorption point are related by a simple power law.

Magnetically induced topological transitions of hyperbolic dispersion in biaxial gyrotropic media

Magnetically induced topological transitions of isofrequency surfaces of bulk waves propagating through an unbounded biaxial gyrotropic medium are studied. The medium is constructed from a two-component superlattice composed of magnetized ferrite and semiconductor layers. To derive the constitutive parameters of the gyrotropic medium, a homogenization procedure from the effective medium theory is applied. The study is carried out in the frequency range near the frequency of ferromagnetic resonance, where the magnetic subsystem possesses the properties of natural hyperbolic dispersion. The topological transitions from an open type-I hyperboloid to several intricate hyperbolic-like forms are demonstrated for the extraordinary waves. We reveal how realistic material losses change the form of isofrequency surfaces characterizing hyperbolic dispersion. The obtained results broaden our knowledge on the possible topologies of isofrequency surfaces that can appear in gyrotropic media influenced by an external static magnetic field.

Reflectance and magneto-optical Kerr rotation of Graphene/SiC/InSb/SiC/Al structure at terahertz frequency region

In this paper, a numerical study on the reflectance and Kerr rotation spectra of a multilayer structure as Graphene/SiC/InSb/SiC/Al was performed at 2−15 THz frequency region. The whole structure was under an external static magnetic field, which was normal to the surface of the layers. The magnetic field was applied to induce the magneto-optical characteristics of the graphene and InSb layers. The Al layer at the end of the structure was utilized to improve the reflectance coefficient of the structure. The reflectance and Kerr rotation spectra of the structure were calculated using 4 by 4 transfer matrix method, and the effects of the strength of external magnetic field (B), environment temperature (T), and chemical potential of graphene (μc) were investigated on the mentioned spectra. The results showed that resonance behaviors were created in both of the spectra at the few particular frequencies. The most strong resonance was seen near the frequency υ=3.1 THz, and the reflectance coefficient and Kerr rotation angle at this frequency were affected by changing the B, T, and μc. It was revealed that one can obtain a particular reflectance coefficient and Kerr rotation angle at this resonance frequency by simultaneous adjustment of B, T, and μc.

Azimuthal surface waves in cylindrical metal waveguides partially filled by magnetoactive plasma: Analysis of energy transfer

Azimuthal surface waves are well known to be eigenwaves of cylindrical waveguide structures—plasma–dielectric–metal—placed into an external axial static magnetic field. The angular velocity of energy transfer along with the angular group velocity is applied to analyze electromagnetic energy rotation in these structures. Optimal magnitudes of effective azimuthal wavenumbers are determined for which the angular velocity reaches its maximum. The angular velocity is shown to decrease with the increasing absolute value of the azimuthal wavenumber and with the decreasing strength of the external axial static magnetic field.

Giant Goos–Hänchen shift of a reflected spin wave from the ultrathin interface separating two antiferromagnetically coupled ferromagnets

The Goos–Hänchen (GH) shift of a spin wave (SW) reflected from the ultrathin nonmagnetic interface between two antiferromagnetically coupled ferromagnetic materials is theoretically investigated. The analytical formulas of the reflection coefficient and the GH shift are derived. The GH shift as a function of the incident angle, the frequency, the external magnetic field, and the uniform exchange parameter is studied. We show that the uniform static external magnetic field and the uniform exchange parameter have a significant impact on the GH shift. Moreover, a giant negative GH shift, which reaches value three orders of magnitude larger than the wavelength of the SW, is observed. Our results will be applied in magnonics, and provide one who studies the GH shift of the SW theoretically or experimentally with some useful help.

Self-diffusion in ionic liquids with nitrate anion: Effects of confinement between glass plates and static magnetic field

Alkylammonium nitrate protic ionic liquids (ILs), when placed between flat polar borosilicate glass plates, have demonstrated enhanced diffusivity and the gradual decrease of diffusivity after exposure to an external static magnetic field (Filippov et al., 2018). This phenomenon has been explained by phase transformations taking place in the ILs. In this study, we observed similar processes occurring in systems prepared with ethylammonium nitrate confined between quartz plates. A higher content of silicon oxide in the plates does not significantly alter the phenomenon previously found in the system prepared with borosilicate glass plates. For the first time, we have observed similar effects of confinement and magnetic field on the aprotic IL, 1‑ethyl‑3‑methylimidazolium nitrate. Substitution of the ethylammonium cation with a 1‑ethyl‑3‑methylimidazolium cation slows down the kinetics and increases magnitude of the processes occurring in the IL exposed to a magnetic field. We suggested that the main factor determining these effects is the presence and modification of the hydrogen-bonding network in the studied protic and aprotic ILs. The process of inverse phase transformation for the confined ethylammonium nitrate after removing the sample from the magnetic field was observed and analysed.

Boosting Backward Raman Amplification Performance Using an External Magnetic Field

This article presents a method of improving backward Raman amplification performance via the addition of an external static magnetic field longitudinal to the laser propagation direction. Our simulation results show that when the laser intensity is low, the output seed intensity can be increased by applying an external magnetic field and a right circularly polarized laser pulse. When the laser intensity is high, the magnetic field increases the self-phase modulation instability and decreases the output seed intensity. In such cases, a left circularly polarized laser pulse can suppress self-phase modulation instability and improve amplification performance. Dynamically adjusting the magnetic field, i.e., by using a double-pass scheme, can combine these two advantages and further improve the output seed intensity.

Manipulation of the zero-damping conditions and unidirectional invisibility in cavity magnonics

In this paper, we report a cavity magnonic system consisting of a split-ring resonator coupled with a yttrium iron garnet sphere, in which both coherent and dissipative coupling strengths can be tuned continuously, thereby making the zero damping conditions (ZDCs) controllable in a frequency range up to 100 MHz. Unidirectional invisibility has been observed under the ZDCs, with the microwaves freely transmitted in the forward direction (−2.9 dB) but almost completely blocked in the backward direction (−83 dB). The effective isolation ratio reaches up to 80 dB, which has surpassed the ideal isolation ratio limited by the state-of-the-art technique, and its direction is reversible by the orientation of the external static magnetic field. As an unconventional nonreciprocal device with flexibility and sensitivity, our magnonic device may open a promising way for robust coherent and quantum information processing.

Magnetic dissipation of near-wall turbulent coherent structures in magnetohydrodynamic pipe flows.

Relaminarization of wall-bounded turbulent flows by means of external static magnetic fields is a long-known phenomenon in the physics of electrically conducting fluids at low magnetic Reynolds numbers. Despite the large literature on the subject, it is not yet completely clear what combination of the Hartmann (M) and the Reynolds number has to be used to predict the laminar-turbulent transition in channel or pipe flows fed by upstream turbulent flows free of magnetic perturbations. Relying upon standard phenomenological approaches related to mixing length and structural concepts, we put forward that M/R_{τ}, where R_{τ} is the friction Reynolds number, is the appropriate controlling parameter for relaminarization, a proposal which finds good support from available experimental data.

Particle Size Controlled Magnetic Loss in Magnetite Nanoparticles in RF-Microwave Region

Frequency-dependent complex magnetic permeability (μ*) is used to understand RF-microwave behaviour of magnetic nanoparticles in the frequency range 250 MHz to 3 GHz. Four stable dispersions of Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> nanoparticles with mean size varying between 11 and 16 nm are prepared for this purpose. The effect of mean particle size and external static magnetic field over dielectric properties of magnetic fluid is studied. The results are explained in the aspect of relaxation and resonance as a consequence of interaction of electromagnetic wave with magnetic fluid. The frequency of ferrimagnetic resonance (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">res</sub> ) and frequency of maximum absorption (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> ) increases to higher frequency as the mean particle size increases in the fluid. The maximum loss tangent (tan δ) increases, and minimum reflection loss (RL) decreases with mean particle size. The f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">res</sub> , f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> , and the maximum tan δ is observed to increase by 55.6%, 15%, and 25.2%, respectively, and minimum RL is observed to decrease by 34.5% by increasing the mean size of Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> nanoparticles from approximately 11 to 16 nm in magnetic fluid. By the application of external static magnetic field, structural arrangements of Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> nanoparticles can be induced in the fluid. The dielectric properties μ*, tan δ, and RL are reported for increasing field strength 0-915 Oe. The effect of increasing field strength on these properties is also size dependent. As the field strength increases, f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">res</sub> shifts to higher frequencies and the spreading bandwidth is comparatively larger for fluid with the highest mean particle size. The maximum tan δ drops as the field strength increases in the fluid with the highest mean particle size while it raises up to critical field strength then onwards it decreases in the fluid with the lowest mean particle size. The mean particle size and mean anisotropy constant affect the field profiles of dielectric propertiesproperties of the magnetic fluid. This kind of study can be useful for radio-microwave devices like tunable attenuator, EM sheilder, and other microwavemicrowave heating application like hyperthermia.

Impact of the tilted magnetic field on the propagation of oblique waves in the plasma superlattice

In its most general statement, we consider the problem of the impact of the external magnetic field on photonic properties of the superlattice comprising dielectric and conducting layers: the direction of the wave propagation as well as the direction of the external magnetic field are assumed to be arbitrary. We show that even a relatively weak external magnetic field can drastically alter the photonic spectrum of the superlattice, since within the photonic gaps there emerge photonic bands making the superlattice transparent for incident radiation. We demonstrate that the spectral width of photonic bands can be effectively controlled by rotation of the static external magnetic field.

Valley-Hall Topological Plasmons in a Graphene Nanohole Plasmonic Crystal Waveguide

We demonstrate that unidirectional and backscattering immune propagation of terahertz optical waves can be achieved in a topological valley-Hall waveguide made of graphene nanohole plasmonic crystals. In order to gain deeper physical insights into these phenomena, the band diagram of graphene nanohole plamsonic crystals has been investigated and optimized. We found that a graphene plasmonic crystal with nanohole arrays belonging to the $C_{6v}$ symmetry group possesses gapless Dirac cones, which can be gapped out by introducing extra nanoholes such that the symmetry point group of the system is reduced from $C_{6v}$ to $C_{3v}$. Taking advantage of this feature, we design a mirror symmetric domain-wall interface by placing together two optimized graphene plasmonic crystals so as to construct valley-polarized topological interface modes inside the opened bandgap. Our computational analysis shows that the valley-Hall topological domain-wall interface modes can be achieved at an extremely deep subwavelength scale, and do not rely on the application of external static magnetic fields. This work may pave a new way to develop highly-integrated and robust terahertz plasmonic waveguides at deep-subwavelength scale.

Magnetically actuated bone scaffold: Microstructure, cell response and osteogenesis

Most of the existing scaffolds do not provide physical stimulation to cells in scaffold-guided bone regeneration. In this work, a superparamagnetic scaffold was fabricated using selective laser sintering with polyglycolic acid as matrix and Fe3O4 nanoparticles as internal magnetic source. Additionally, a self-developed external static magnetic field (SMF) was used to provide external magnetic source. In this case, the magnetic moment of the Fe3O4 nanoparticles rearranged along the direction of SMF, thereby generating a locally enhanced magnetic field. The enhanced magnetic field might directly stimulate cell surface receptors and activate downstream signaling pathways. As a consequence, the human umbilical cord-derived mesenchymal stem cells cultivated in the scaffold exhibited significantly enhanced gene expression of alkaline phosphatase, osteocalcin, type I collagen and runt-related transcription factor-2. In vivo tests revealed that the bone regeneration was accelerated with bone mineral density (with SMF: 515 ± 50 mg/cc, without SMF: 326 ± 15 mg/cc), percentage of bone volume/tissue volume (with SMF: 92 ± 3.5%, without SMF: 73 ± 5.2%) and new bone area fraction (with SMF: 86 ± 2.2%, without SMF: 70 ± 1.6%) after 8 weeks' implantation. The biodistribution and serum biochemistry analysis demonstrated that superparamagnetic scaffold possessed favorable biosafety.

Effect of Landau damping on ion acoustic solitary waves in a collisionless unmagnetized plasma consisting of nonthermal and isothermal electrons

We have used the Sagdeev pseudo-potential technique to investigate the arbitrary amplitude ion acoustic solitons, double layers and supersolitons in a collisionless magnetized plasma consisting of adiabatic warm ions, isothermal cold electrons and nonthermal hot electrons immersed in an external uniform static magnetic field. We have used the phase portraits of the dynamical system describing the nonlinear behaviour of ion acoustic waves to confirm the existence of different solitary structures. We have also investigated the transition of different solitary structures: soliton (before the formation of double layer) $\rightarrow$ double layer $\rightarrow$ supersoliton $\rightarrow$ soliton (soliton after the formation of double layer) by considering the variation of $\theta$ only, where $\theta$ is the angle between the direction of the external uniform static magnetic field and the direction of propagation of the wave.

Vector-boson condensates, spin-triplet superfluidity of paired neutral and charged fermions, and 3P2 pairing of nucleons

After reminding of properties of the condensate of the complex scalar field in the external uniform magnetic field $H$ focus is made on the study of phases of the complex neutral vector boson fields coupled with magnetic field by the Zeeman coupling and phases of the charged vector boson fields. These systems may behave as nonmagnetic and ferromagnetic superfluids and ordinary and ferromagnetic superconductors. Response of the ferromagnetic superfluid and superconducting systems occupying half of space on the external uniform static magnetic field $H$ is thoroughly studied. Then the spin-triplet pairing of neutral fermions at conserved spin is considered. Novel phases are found. In external magnetic field the phase with zero mean spin proves to be unstable to the formation of a phase with a non-zero spin. For $H>H_{\rm cr 2}$ the spin-triplet pairing and ferromagnetic superfluidity continue to exist above the "old" phase transition critical temperature $T_{\rm cr}$. For a certain parameter choice ferromagnetic superfluid phases are formed already for $H=0$, characterized by an own magnetic field $h$. Formation of domains is discussed. Next, spin-triplet pairing of charged fermions is studied. Novel phases are found with a ferromagnetic superconductivity. Then, the 3P$_2$ $nn$ pairing in neutron star matter is studied. Also a 3P$_2$ $pp$ pairing is considered. Numerical estimates are performed in the BCS weak coupling limit and beyond it for the $3P_2$ $nn$ and $pp$ pairings, as well as for the 3S$_1$ $np$ pairing.

Solitary self‐gravitational potential in magnetized astrophysical degenerate quantum plasmas

A rigorous theoretical investigation has been conducted on solitary self‐gravitational potential structures in a magnetized degenerate quantum plasma system (containing heavy nuclei and degenerate electrons). The reductive perturbation method has been used to derive the Korteweg‐de Vries (K‐dV) equation, which admits a solitary wave solution for small but finite amplitude limit. It has been shown, for the first time, that the periodic U‐shaped structures represented by secant square function [Asaduzzaman et al, Physics of Plasmas, 24, 052102 (2017)] are converted into solitary self‐gravitational potential structures represented by hyperbolic secant square function due to the presence of a static external magnetic field. It is also observed that the effects of the static external magnetic field and obliqueness significantly modify the basic properties (viz. amplitude, width, speed, etc.) of the solitary self‐gravitational potential structures.

Rotation of electromagnetic energy initiated by azimuthal surface waves in coaxial metal waveguides entirely filled by plasma

Azimuthal surface waves are well-known to be eigenwaves of coaxial metal waveguides entirely filled by plasma. The present study of electromagnetic energy transfer complements the investigation of the wave dispersion properties carried out earlier. The angular velocity of energy transfer is analyzed as a function of the coaxial-line parameters and compared with three limiting cases. One case is a metal waveguide entirely filled by plasma. The second case is a metal rod placed into infinite plasma along an external static magnetic field. Finally, the third one is a thin coaxial waveguide.