Zitterbewegung in quantum field theory

Traditionally, the zitterbewegung （ZB） of the Dirac electron has just been studied at the level of quantum mechanics. Seeing the fact that an old interest in ZB has recently been rekindled by the investigations on spintronic, graphene, and superconducting systems, etc., this paper presents a quantum-field-theory investigation on ZB and obtains the conclusion that, the ZB of an electron arises from the influence of virtual electron-positron pairs （or vacuum fluctuations） on the electron.

Ferromagnetic-insulators-modulated transport properties on the surface of a topological insulator

Transport properties on the surface of a topological insulator （TI） under the modulation of a two-dimensional （2D） ferromagnet/ferromagnet junction are investigated by the method of wave function matching. The single ferromagnetic barrier modulated transmission probability is expected to be a periodic function of the polarization angle and the planar rotation angle, that decreases with the strength of the magnetic proximity exchange increasing. However, the transmission probability for the double ferromagnetic insulators modulated n-n junction and n-p junction is not a periodic function of polarization angle nor planar rotation angle, owing to the combined effects of the double ferromagnetic insulators and the barrier potential. Since the energy gap between the conduction band and the valence band is narrowed and widened respectively in ranges of 0 ≤ 0 〈π/2 and r/2 〈 0 ≤ π, the transmission probability of the n-n junction first increases rapidly and then decreases slowly with the increase of the magnetic proximity exchange strength. While the transmission probability for the n-p junction demonstrates an opposite trend on the strength of the magnetic proximity exchange because the band gaps contrarily vary. The obtained results may lead to the possible realization of a magnetic/electric switch based on TIs and be useful in further understanding the surface states of TIs.

Measurement of the electronic structure of a type-Ⅱ topological Dirac semimetal candidate VAI_(3) using angle-resolved photoelectron spectroscopy

Type-Ⅱ topological Dirac semimetals are topological quantum materials hosting Lorentz-symmetry breaking type-Ⅱ Dirac fermions,which are tilted Dirac cones with various exotic physical properties,such as anisotropic chiral anomalies and novel quantum oscillations.Until now,only limited material systems have been confirmed by theory and experiments with the type-Ⅱ Dirac fermions.Here,we investigated the electronic structure of a new type-Ⅱ Dirac semimetal VA1_(3) with angle-resolved photoelectron spectroscopy.The measured band dispersions are consistent with the theoretical prediction,which suggests the Dirac points are located close to(at about 100 meV above) the Fermi level.Our work demonstrates a new type-Ⅱ Dirac semimetal candidate system with different Dirac node configurations and application potentials.

A Physical Insight into the Origin of the Corrections to the Magnetic Moment of Free and Bound Electron

The main goal of the present work is a unitary approach of the physical origin of the corrections to the magnetic moment of free and bound electron. Based on this approach, estimations of lowest order corrections were easily obtained. In the non-relativistic limit, the Dirac electron appears as a distribution of charge and current extended over a region of linear dimension of the order of Compton wavelength, which generates its magnetic moment. The e.m. mass (self-energy) of electron outside this region does not participate to this internal dynamics, and consequently does not contribute to the mass term in the formula of the magnetic moment. This is the physical origin of the small increase of the magnetic moment of free electron compared to the value given by Dirac equation. We give arguments that this physical interpretation is self-consistent with the QED approach. The bound electron being localized, it has kinetic energy which means a mass increase from a relativistic point of view, which determines a magnetic moment decrease (relativistic Breit correction). On the other hand, the e.m. mass of electron decreases at the formation of the bound state due to coulomb interaction with the nucleus. We estimated this e.m. mass decrease of bound electron only in its internal dynamics region, and from it the corresponding increase of the magnetic moment (QED correction). The corrections to the mass value are at the origin of the lowest order corrections to the magnetic moment of free and bound electron.

On Zitterbewegung of Electron

Traditionally, all the discussions relativistic quantum mechanics. In this article, on zitterbewegung （zbw） of electron are based on from the viewpoint of quantum field theory and in terms of the creation and annihilation operators as well as the polarization vectors of spin-1 field, a more detailed description and some new perspectives for zbw are obtained. Especially, it is shown that zbw arises from a to-and-fro vacuum polarization that occurring in the neighborhood of electron; the zbw vectors form a vector triplet with total spin projections 0 and ±1 in the direction of the momentum of electron, respectively; the macroscopic velocity of the vacuum medium vanishes in all inertial systems.

Microscopic calculation of the magnetic field of neutron stars

Based on the Dirac equation describing an electron moving in a uniform and cylindrically symmetric magnetic field which may be the result of the self-consistent mean field of the electrons themselves in a neutron star, we have obtained the eigen solutions and the orbital magnetic moments of electrons in which each eigen orbital can be calculated. From the eigen energy spectrum we find that the lowest energy level is the highly degenerate orbitals with the quantum numbers pz = 0, n = 0, and m ≥0. At the ground state, the electrons fill the lowest eigen states to form many Landau magnetic cells and each cell is a circular disk with the radius λfree and the thickness λe, where λfree is the electron mean free path determined by Coulomb cross section and electron density and λe is the electron Compton wavelength. The magnetic moment of each cell and the number of cells in the neutron star are calculated, from which the total magnetic moment and magnetic field of the neutron star can be calculated. The results are compared with the observational data and the agreement is reasonable.