Electron In Electromagnetic Field Research Articles

Anomaly in the electron orbital gyromagnetic factor: QED and radiative interactions

Using standard Quantum Electrodynamics (QED), we have calculated the anomaly in the electron orbital g-factor, which is in reasonable agreement with experimental data. For second-order corrections, the anomaly in the orbital g-factor is of the order α/3π, while for approximations to the same order, the well-known anomaly in the electron spin g-factor where α = 1/137 is the structure constant. Unlike the spin-g anomaly, the orbital-g anomaly is not intrinsic, but depends on the atomic state, and on Z, the atomic mass. Thus, the orbital anomaly is actually (α/3π)D, where D includes the effect of the magnetic field and/or the atomic properties. Hence, we have shown that radiative interactions, which are the sources of the spin-g anomaly, also produce an orbital anomaly. It is physically reasonable to expect that radiative interactions that modify many physical properties of electrons in electromagnetic fields will also modify the orbital magnetic moment of the electron.

Linear magnetoresistance induced by intra-scattering semiclassics of Bloch electrons

The weak field magnetoresistance has seen a revived interest due to the distinct role played by the momentum-space Berry curvature of Bloch electrons. While most previous studies in this regard focus on the inter-scattering motion of semiclassical Bloch electrons in electromagnetic fields, the intra-scattering effects of the semiclassical dynamics augmented by the Berry curvature, magnetic moment and shift vector on the magnetoresistance have been largely overlooked. Here we uncover that these intra-scattering effects, which are neglected in the field-independent relaxation time approximation to the Boltzmann collision integral, can be as important as the inter-scattering ones. Concrete calculations on the two dimensional gapped Dirac model show that the sign of the negative linear magnetoresistance given by the Berry curvature alone is reversed when one considers the magnetic moment and shift vector.

Dirac donor states controlled by magnetic field in gapless and gapped graphene

In this paper, the exact solutions of Dirac electronic states of graphene in Coulomb and magnetic fields are acquired. The Coulomb field not only causes the splitting of Landau levels in gapless graphene but also leads to the variation of the energy level ordering in gapped graphene. The dependence of the binding energies on the gap and the magnetic field is discussed. Furthermore, the valley degree of freedom and the valley splitting spacing can be controlled by the Coulomb and magnetic fields in gapped graphene. The intervalley mixing of graphene is estimated and calculated in the direct sum spaces of the two valleys. The results obtained help us to understand the behaviors of the planar Dirac electron in electromagnetic fields and can be applied to the controlling of the electron's behaviors in graphene.

Introduction to Nonequilibrium Statistical Mechanics with Quantum Field Theory

In this article, we present a concise and self-contained introduction to nonequilibrium statistical mechanics with quantum field theory by considering an ensemble of interacting identical bosons or fermions as an example. Readers are assumed to be familiar with the Matsubara formalism of equilibrium statistical mechanics such as Feynman diagrams, the proper self-energy, and Dyson's equation. The aims are threefold: (i) to explain the fundamentals of nonequilibrium quantum field theory as simple as possible on the basis of the knowledge of the equilibrium counterpart; (ii) to elucidate the hierarchy in describing nonequilibrium systems from Dyson's equation on the Keldysh contour to the Navier-Stokes equation in fluid mechanics via quantum transport equations and the Boltzmann equation; (iii) to derive an expression of nonequilibrium entropy that evolves with time. In stage (i), we introduce nonequilibrium Green's function and the self-energy uniquely on the round-trip Keldysh contour, thereby avoiding possible confusions that may arise from defining multiple Green's functions at the very beginning. We try to present the Feynman rules for the perturbation expansion as simple as possible. In particular, we focus on the self-consistent perturbation expansion with the Luttinger-Ward thermodynamic functional, i.e., Baym's Phi-derivable approximation, which has a crucial property for nonequilibrium systems of obeying various conservation laws automatically. We also show how the two-particle correlations can be calculated within the Phi-derivable approximation, i.e., an issue of how to handle the "Bogoliubov-Born-Green-Kirkwood-Yvons (BBGKY) hierarchy".

Atomic systems with one and two active electrons in electromagnetic fields: Ionization and high harmonics generation

We describe a theoretical procedure for solving the time-dependent Schrödinger equation (TDSE) for atomic systems with one or two valence electrons. Motion of the valence electrons is described by means of the Hartree-Fock potential including the exchange interaction. We apply the procedure to various physical phenomena occurring in atoms exposed to strong electromagnetic fields. As an illustration, we consider below the processes of high harmonics generation and attosecond pulses production.

A new approach on studying electron behavior under very intense laser beam

The recent emergence of the field studying interactions between very intense laser fields and charged particles, brings about the problem of determining if, and under what conditions, the quantum equations which describe these interactions are at the classical limit. We present an affirmative answer to this question in the case of an electron in electromagnetic field, corresponding to intensities of the electrical field of the order one atomic unit, or greater. We neglect the spin interactions, and show that with very good approximation (the relative error being less than 10/sup -7/), the solution of the Klein-Gordon equation is a function only of the classical action S, written for the same system. Our approach does not use the semiclassical approximation, and it implies that the solution of the Klein-Gordon equation is at the classical limit of quantum mechanics for the systems discussed here. The results lead to a simplified computational model for analysing these systems.

Berry's Phase of Bloch Electrons in Electromagnetic Fields

Berry recognized in quantum mechanics a topological phase factor arising from the adiabatic transport of a system around a closed loop, which is essentially the Aharonov-Bohm effect in parameter space. In this paper we consider noninteracting electrons in a periodic potential in the presence of electromagnetic fields. The electric field is represented by a time-dependent vector potential. Adiabatic processes move states along a non-contractible closed loop in the magnetic Brillouin zone which is a torus. The existence of Berry's phases in such processes is shown. A relation with the quantized Hall effect is discussed.

New Phototubes and Photomultipliers Resistive against High Magnetic Fields

The energy of particles in recent high energy physics experiments has been increasing, so that detector apparatus is inevitably placed in high magnetic field environment. Therefore new photodetectors are required which, unlike conventional photomultipliers, are inherently insensitive to high magnetic fields. We have developed four types of new photodetector for the use in high magnetic fields: a one-atm. xenon filled phototube, a rectangular vacuum photodiode, a one-stage photomultiplier and a photomultiplier with fine-mesh dynodes. Each of them is specially designed on the basis of the analysis of the behavior of electrons in electromagnetic fields and is capable of stable operation in magnetic fields as high as several kilogauss or more.

Solutions for the motion of an electron in electromagnetic fields

New exact solutions of the Lorentz, Hamilton-Jacobi, Klein-Gordon, and Dirac equations for an electron moving in the field of a plane wave and in electric and magnetic fields have been found. The electric and magnetic fields are parallel to the direction of propagation of the plane wave. The magnetic field is constant and the electric field is an arbitrary function of the combination $ct\ensuremath{-}z$.

The motion of an electron in electromagnetic fields of special form

The motion of an electron in electromagnetic fields of special form