Strong Magnetic Field Regime Research Articles

Magnetic-field-dependent electric-charge transport in hadronic medium at finite temperature

Electric charge transport of hadronic matter at finite temperature and magnetic field is studied within the linear sigma model. Anisotropic transport coefficients associated with the charge transport are estimated both in the weak and strong regimes of the magnetic field using the transport theory approach. In a weakly magnetized medium, the magnetic field effects are incorporated through the Lorentz force term in the Boltzmann equation. Strong magnetic field puts further constraints on the motion of charged particles through Landau quantization. Magnetic field-dependent thermal relaxation time is obtained from interaction rates of hadrons with the S-matrix approach by considering the Landau level kinematics of the charged hadrons. Mean-field effects are embedded in the analysis through the temperature-dependent hadron masses. Further, the hadronic medium response to a time-varying external electric field is studied in weak and strong magnetic field regimes. It is seen that electromagnetic responses of the hadronic matter have a strong dependence on the mean-field effects, sigma mass, the strength of the external fields, and its evolution in the medium.

Electric field influenced coordinate jump of the guiding centre and magnetotransport

ABSTRACT Our studies formulate a classical theory to study the influence of in-plane electric field on electron-impurity scattering process and magnetotransport in a two-dimensional space, in the presence of a strong out-of-plane magnetic field. Our studies connect classical scattering and quantum Landau Level broadening, as will be reviewed in this report. We derived an electric current formula in agreement with the current derived from the Drude theory under a strong magnetic field. Our electric current formula is derived microscopically from the migration of the guiding centres at strong magnetic field regime . The electron-impurity scattering under electromagnetic field not only shifts the guiding centre coordinates X and Y, but also changes cyclotron radius R. The change of cyclotron radius R compensates the change of the electric potential energy during the scattering process. The broadening of cyclotron radius is a classical manifestation of Landau Levels broadening. Our conductivity derived from our current formula in the linear response regime results in the same as the current derived from Kubo current fluctuation theory, providing a special case of the fluctuation-dissipation theorem.

Electric Field Influenced Coordinate Jump of the Guiding Center and Magnetotransport

We derived an electrical current formula in the presence of a strong out of plane magnetic field and an in plane electric field, and within two dimensional disordered systems. This current is originated from the guiding center coordinate jump. At a strong magnetic field regime, the current can be pictured as the migration of the center coordinates. During the electron impurity scattering, the guiding centers suddenly shift their coordinates. Because of the electric field, the coordinate shift accumulatively contributes to a longitudinal current. During the scattering, the value of cyclotron radius changes, which compensates for the change of the electric potential energy during the coordinate jump. The diversion of cyclotron radius is the classical manifestation of electric field dependent broadening and shifting of the Landau levels.

Operator lifetime and the force-free electrodynamic limit of magnetised holographic plasma

Using the framework of higher-form global symmetries, we examine the regime of validity of force-free electrodynamics by evaluating the lifetime of the electric field operator, which is non-conserved due to screening effects. We focus on a holographic model which has the same global symmetry as that of low energy plasma and obtain the lifetime of (non-conserved) electric flux in a strong magnetic field regime. The lifetime is inversely correlated to the magnetic field strength and thus suppressed in the strong field regime.

Spectrum Collapse of Disordered Dirac Landau Levels as Topological Non-Hermitian Physics

We investigate disorder effects on Landau levels in Dirac electron systems with the use of a non-Hermitian quasiparticle Hamiltonian formalism. This formalism reveals that spin-dependent scattering rates induce the spectrum collapse of Landau levels, i.e., the disappearance of the energy gaps between n-th and -n-th levels under a finite external magnetic field. The spectrum collapse occurs in both weak and strong magnetic field regimes, thus showing a reentrant behavior. Particularly, in the strong magnetic field regime, in contrast to naive expectation, the increase of a magnetic field stabilizes the spectrum collapse of Dirac Landau levels. Furthermore, it is revealed that the spectrum collapse is associated with the emergence of a vortex texture with a topological winding number of a complex energy spectrum of the non-Hermitian system.

Longitudinal magnetoconductivity of tilted type-I Weyl semimetals from semiclassical to ultra-quantum regime

Weyl semimetals (WSMs) display many unusual magnetotransport phenomena. Here, based on the Landau quantization and Boltzmann equation, we theoretically study the longitudinal magnetoconductivity for tilted type-I WSMs from weak to strong magnetic field within a unified framework. It is found that, in semiclassical (weak magnetic field) regime, the conductivity has an angular dependent B-linear term besides the B-quadratic term common to isotropic nodes. In ultra-quantum (strong magnetic field) regime, the magnetoconductivity shows a linear dependence on B, and this dependence is affected by the tilt. In the intermediate regime, magnetoconductivity shows a tilt-modified quantum oscillation behavior due to the oscillation in the density of state. These findings recover the results for isotropic nodes without tilt, and suggest a possible way to identify the tilt axis of tilted WSMs through magnetotransport experiment.

Nonlinearity of the zigzag graphene nanoribbons with antidots via the f-deformed Dirac oscillator in (2+1)-dimensions

We study the nonlinearity for the zigzag graphene nanoribbons (ZGNRs) with zigzag triangular holes (ZTHs). We show that in the presence of an external uniform magnetic field, a two-dimensional f-deformed Dirac oscillator can be used to describe the dynamics of the electrons in the ZGNRs with ZTHs. It is shown for the first time that the magnetic field direction has effect on the chirality of charge carriers in the ZGNRs punched with triangular holes. We also obtain the Landau-level spectrum in the weak and strong magnetic field regimes. Additionally, we compare Landau-level spectrum of this graphene-based device in the f-deformed scenario and original one. Our results provide a general viewpoint for the development of the zigzag graphene nanoribbons.

The (2+1)-dimensional f-deformed Dirac oscillator in the presence of an external field

We consider a two-dimensional f-deformed Dirac oscillator in the presence of an external uniform static magnetic field. We show that the two-dimensional f-deformed Dirac oscillator maps exactly onto the anti-Jaynes–Cummings (AJC) and Jaynes–Cummings (JC) models. We also obtain the energy spectrum and corresponding eigenstates in the weak and strong magnetic field regimes. We show how the change in chirality is associated with the magnitude of the magnetic field. We investigate the two-dimensional f-deformed Dirac oscillator in an external (isospin) field and find its energy spectrum.

High precision hyperfine measurements in Bismuth challenge bound-state strong-field QED

Electrons bound in highly charged heavy ions such as hydrogen-like bismuth 209Bi82+ experience electromagnetic fields that are a million times stronger than in light atoms. Measuring the wavelength of light emitted and absorbed by these ions is therefore a sensitive testing ground for quantum electrodynamical (QED) effects and especially the electron–nucleus interaction under such extreme conditions. However, insufficient knowledge of the nuclear structure has prevented a rigorous test of strong-field QED. Here we present a measurement of the so-called specific difference between the hyperfine splittings in hydrogen-like and lithium-like bismuth 209Bi82+,80+ with a precision that is improved by more than an order of magnitude. Even though this quantity is believed to be largely insensitive to nuclear structure and therefore the most decisive test of QED in the strong magnetic field regime, we find a 7-σ discrepancy compared with the theoretical prediction.

Anisotropic magnetoresistance and piezoelectric effect in GaAs Hall samples

In this work, we argue that an anisotropic interaction potential may stabilize anisotropic liquid phases of electrons even in a strong magnetic field regime where normally one expects to see only isotropic quantum Hall or isotropic Fermi liquid states. We use this approach to support a theoretical framework that envisions the possibility of an anisotropic liquid crystalline state of electrons in the lowest Landau level. In particular, we argue that an anisotropic liquid state of electrons may stabilize in the lowest Landau level close to the liquid-solid transition region at filling factor $\nu=1/6$ for a given anisotropic Coulomb interaction potential. Quantum Monte Carlo simulations for a liquid crystalline state with broken rotational symmetry indicate stability of liquid crystalline order consistent with the existence of an anisotropic liquid state of electrons stabilized by anisotropy at filling factor $\nu=1/6$ of the lowest Landau level.

Strain induced novel quantum magnetotransport properties of topological insulators

Recent theoretical and experimental researches have revealed that the strained bulk HgTe can be regarded as a three-dimensional topological insulator (TI). Motivated by this, we explore the strain effects on the transport properties of the HgTe surface states, which are modulated by a weak 1D in-plane electrostatic periodic potential in the presence of a perpendicular magnetic field. We analytically derive the zero frequency (dc) diffusion conductivity for the case of quasielastic scattering in the Kubo formalism, and find that, in strong magnetic field regime, the Shubnikov–de Haas oscillations are superimposed on top of the Weiss oscillations due to the electric modulation for null and finite strain. Furthermore, the strain is shown to remove the degeneracy in inversion symmetric Dirac cones on the top and bottom surfaces. This accordingly gives rise to the splitting and mixture of Landau levels, and the asymmetric spectrum of the dc conductivity. These phenomena, not known in a conventional 2D electron gas and even in a strainless TI and graphene, are a consequence of the anomalous spectrum of surface states in a fully stained TI. These results should be valuable for electronic and spintronic applications of TIs, and thus we fully expect to see them in the further experiment.

De Haas-van Alphen oscillations for neutral atoms in electric fields

In this work we study the de Haas van Alfhen (dHvA) effect for neutral atoms with a nonvanishing magnetic moment interacting with an electric field. Considering the particles confined in a two dimensional (2D) atomic cloud and using the Landau-Aharonov-Casher (LAC) theory, we obtain the effective magnetic field as well as the energy eigenfunctions and eigenvalues of the system. Assuming the neutral atoms as being $ ^{87}\mathrm{Rb} $ ultracold Rydberg atoms we calculate the degeneracy of the energy levels. Under a strong effective magnetic field regime we present the quantum oscillations in the energy and effective magnetization of the atomic gas. From the dHvA period we determine the area of the Fermi circle of the atomic cloud.

Effects of crossed electric and magnetic fields on the interband optical absorption spectra of variably spaced semiconductor superlattices

The interband optical absorption spectra of a GaAs–Ga1−xAlxAs variably spaced semiconductor superlattice under crossed in-plane magnetic and growth-direction applied electric fields are theoretically investigated. The electronic structure, transition strengths and interband absorption coefficients are analyzed within the weak and strong magnetic-field regimes. A dramatic quenching of the absorption coefficient is observed, in the weak magnetic-field regime, as the applied electric field is increased, in good agreement with previous experimental measurements performed in a similar system under growth-direction applied electric fields. A decrease of the resonant tunneling in the superlattice is also theoretically obtained in the strong magnetic-field regime. Moreover, in this case, we found an interband absorption coefficient weakly dependent on the applied electric field. Present theoretical results suggest that an in-plane magnetic field may be used to tune the optical properties of variably spaced semiconductor superlattices, with possible future applications in solar cells and magneto-optical devices.

Mechanical strain induced valley-dependent quantum magnetotransport of Dirac particles in graphene

We have explored the mechanical strain effects on the magnetotransport in graphene with a 1D electrostatic periodic potential in the presence of a perpendicular magnetic field. We find that, in a strong magnetic field regime, the conductivity exhibits a superposition of the Shubnikov–de Haas and Weiss oscillations in each valley due to the electrical modulation. Especially, the strain removes the valley degeneracy of Landau levels in inversion symmetric Dirac cones. Accordingly, this causes the valley-dependence of the conductivity. These phenomena, absent in a freestanding graphene, are a consequence of the anomalous spectrum of carriers in a fully stained graphene.

Weak magnetic field effects on chiral critical temperature in a nonlocal Nambu–Jona-Lasinio model

In this paper we study the nonlocal Nambu–Jona-Lasinio model with a Gaussian regulator in the chiral limit. Finite temperature effects and the presence of a homogeneous magnetic field are considered. The magnetic evolution of the critical temperature for chiral symmetry restoration is then obtained. Here, we restrict ourselves to the case of low magnetic field values, being this a complementary discussion to the existing analysis in nonlocal models in the strong magnetic field regime.

An improved value for the hyperfine splitting of hydrogen-like 209Bi82+

We report an improved measurement of the hyperfine splitting in hydrogen-like bismuth (209Bi82+) at the experimental storage ring ESR at GSI by laser spectroscopy on a coasting beam. Accuracy was improved by about an order of magnitude compared to the first observation in 1994. The most important improvement is an in situ high voltage measurement at the electron cooler (EC) platform with an accuracy at the 10 ppm level. Furthermore, the space charge effect of the EC current on the ion velocity was determined with two independent techniques that provided consistent results. The result of nm provides an important reference value for experiments testing bound-state quantum electrodynamics in the strong magnetic field regime by evaluating the specific difference between the splittings in the hydrogen-like and lithium-like ions.

Confinement effects of magnetic field on two-dimensional hydrogen atom in plasmas

In this study, for the first time, the Schrödinger equation with more general exponential cosine screened Coulomb (MGECSC) potential is solved numerically in the presence and in the absence of an external magnetic field within two-dimensional formalism using the asymptotic iteration method. The MGECSC potential includes four different potential forms when considering different sets of the parameters in the potential. The plasma screening effects in the weak and strong magnetic field regimes as well as the confinement effects of magnetic field on the two-dimensional hydrogen atom in Debye and quantum plasmas are investigated by solving the corresponding equations. It is found that applying a uniform magnetic field on the hydrogen atom embedded in a plasma leads to change in the profile of the total interaction potential. Thus, confinement effects of magnetic field on hydrogen atom embedded in Debye and quantum plasmas modeled by a MGECSC potential lead to shift bound state energies. This effect would be important to isolate the plasma from the external environment in the experimental applications of plasma physics.

Trans-Alfvénic motions in the Taurus molecular cloud

Magnetically aligned velocity anisotropy over varying physical conditions and environments within the Taurus Molecular Cloud is evaluated from analysis of wide field spectroscopic imaging of 12CO and 13CO J=1-0 emission. Such anisotropy is a result of MHD turbulence in the strong magnetic field regime and provides an indirect measure of the role of magnetic fields upon the gas. Velocity anisotropy aligned with the local, projected mean magnetic field direction is limited to fields with low surface brightness 12CO emission corresponding to regions of low visual extinction and presumably, low gas volume density. The more optically thin 13CO J=1-0 emission shows little evidence for velocity anisotropy. We compare our results with computational simulations with varying degrees of magnetic field strength and Alfvenic Mach numbers. In the diffuse, molecular envelope of the cloud, a strong magnetic field and sub-Alfvenic turbulent motions are inferred. Super-Alfvenic motions are present within the high column density filaments of the Taurus cloud. From this trans-Alfvenic flow, we constrain the scaling exponent, kappa, of the magnetic field density relation (B ~ n^kappa) to be near zero as expected for ambipolar diffusion or material loading of magnetic flux tubes.

Quasineutral Limit of the Vlasov-Poisson System with Massless Electrons

In this paper, we study the quasineutral limit (in other words the limit when the Debye length tends to zero) of Vlasov-Poisson like equations describing the behavior of ions in a plasma. We consider massless electrons, with a charge density following a Maxwell-Boltzmann law. For cold ions, using the relative entropy method, we derive the classical Isothermal Euler or the (inviscid) Shallow Water systems from fluid mechanics. We then study the combined quasineutral and strong magnetic field regime for such plasmas.

ELECTROMAGNETIC CASCADES IN MAGNETIZED MEDIA

The investigation of the astrophysical nature of gamma-ray sources and the processes responsible for their broad-band emission requires a detailed modeling of their observable spectrum, in which electromagnetic cascades can play an important role. An open issue in this modeling is the effect of magnetic fields in the development of cascades. In this paper we present a novel numerical scheme to compute this effect in a self-consistent way. Applied to a toy model, our scheme reproduces the features expected for cascades in the strong and weak magnetic field regimes.