Doing Spin Physics with Unpolarized Particles.

Twisted, or vortex, particles refer to freely propagating non-plane-wave states with helicoidal wave fronts. In this state, the particle possesses a nonzero orbital angular momentum with respect to its average propagation direction. Twisted photons and electrons have been experimentally demonstrated, and creation of other particles in twisted states can be anticipated. If brought in collisions, twisted states offer a new degree of freedom to particle physics, and it is timely to analyze what new insights may follow. Here, we theoretically investigate resonance production in twisted photon collisions and twisted e^{+}e^{-} annihilation and show that these processes emerge as a completely novel probe of spin and parity-sensitive observables in fully inclusive cross sections with unpolarized initial particles. This is possible because the initial state with a nonzero angular momentum explicitly breaks the left-right symmetry even when averaging over helicities. In particular, we show how one can produce almost 100% polarized vector mesons in unpolarized twisted e^{+}e^{-} annihilation and how to control its polarization state.

Electric Quadrupole Moment and the Tensor Magnetic Polarizability of Twisted Electrons and a Potential for their Measurements.

For a twisted (vortex) Dirac particle in nonuniform electric and magnetic fields, the relativistic Foldy-Wouthuysen Hamiltonian is derived including high order terms describing new effects. The result obtained shows for the first time that a twisted spin-1/2 particle possesses a tensor magnetic polarizability and a measurable (spectroscopic) electric quadrupole moment. We have calculated the former parameter and have evaluated the latter one for a twisted electron. The tensor magnetic polarizability of the twisted electron can be measured in a magnetic storage ring because a beam with an initial orbital tensor polarization acquires a horizontal orbital vector polarization. The electric quadrupole moment is rather large and strongly influences the dynamics of the intrinsic orbital angular momentum (OAM). Three different methods of its measurements, freezing the intrinsic orbital angular momentum and two resonance methods, are proposed. The existence of the quadrupole moment of twisted electrons can lead to practical applications.

Relativistic Quantum Dynamics of Twisted Electron Beams in Arbitrary Electric and Magnetic Fields.

Relativistic quantum dynamics of twisted (vortex) Dirac particles in arbitrary electric and magnetic fields are constructed for the first time. This allows us to change the controversial contemporary situation when the nonrelativistic approximation is used for relativistic twisted electrons. The relativistic Hamiltonian and equations of motion in the Foldy-Wouthuysen representation are derived. A critical experiment for a verification of the results obtained is proposed. The new important effect of a radiative orbital polarization of a twisted electron beam in a magnetic field resulting in a nonzero average projection of the intrinsic orbital angular momentum on the field direction is predicted.

Manipulating Twisted Electron Beams.

A theoretical description of twisted (vortex) electrons interacting with electric and magnetic fields is presented, based on Lorentz transformations. The general dynamical equations of motion of a twisted electron with an intrinsic orbital angular momentum in an external field are derived. Methods for the extraction of an electron vortex beam with a given orbital polarization and for the manipulation of such a beam are developed.

Distribution Characteristic and Migration Mechanism of Toxic Gases in Goafs during Close-Distance Coal Seam Mining: a Case Study of Shaping Coal Mine.

It is imperative to have an in-depth understanding of the gas migration mechanism during close-distance coal seam mining, not only to prevent fires in the coal industry but also to propose safety strategies for controlling toxic gases. The 1818 working face of the Shaping Coal Mine was used as an exemplary close-distance coal seam mine. Through the construction of boreholes and the arrangement of bundle pipes in the two parallel grooves of the working face and the upper goaf at the corresponding positions in the working face, the gases in the upper and lower goafs were monitored online timely. The firsthand information about the gas distribution was obtained through on-site tests, which provided the robust data for studying the migration mechanism of toxic gases during close-distance coal seam mining. By studying the spatial distribution of harmful gases in the upper goaf without mining the overlying coal, the static distribution law of gas was obtained. By discussing the spatial distribution and migration of harmful gases in the goaf of the overlying coal seam during mining, the dynamic distribution law of the gas was obtained. By studying the spatial distribution and migration of toxic gases in the mined-out area of the lower coal seam during mining, the dynamic distribution of gases in the mined-out area of the lower coal seam was obtained. Moreover, the migration mechanism of gas emission from the goafs in the close-distance coal seam was explored. By analyzing the factors responsible for the accumulation of toxic gases in the return air corner, feasible safety measures were also proposed to prevent this hazard during close-distance coal seam mining.

Self-healing solid polymer electrolyte based on imine bonds for high safety and stable lithium metal batteries.

Due to their low flammability, good dimensional stability and chemical stability, solid polymer electrolytes are currently attracting extensive interest for building lithium metal batteries. But severe safety issues such as cracks or breakage, resulting in short circuits will prevent their widespread application. Here, we report a new design of self-healing solid polymer electrolyte (ShSPE) based on imine bonds, fabricated from varying amounts of polyoxyethylenebis(amine) and terephthalaldehyde through a simple Schiff base reaction. Moreover, adding diglycidyl ether of bisphenol A improves the flexibility and high stretchability of the polymer electrolyte. The polymer networks exhibit good thermal stability and excellent self-healing characteristics. The ShSPE with the highest NH2-PEG-NH2 content (ShSPE-3) has an improved lithium ion transference number of 0.39, and exhibits an electrochemical stability up to 4.5 V vs. Li/Li+. ShSPE-3 shows the highest ionic conductivity of 1.67 × 10-4 S cm-1 at 60 °C. Besides, the interfacial stability of ShSPE-3 is promoted and the electrolyte membrane exhibits good cycling performance with LiFePO4, and the LiFePO4/Li cell exhibits an initial discharge capacity of 141.3 mA h g -1. These results suggest that self-healing solid polymer electrolytes are promising candidates for high safety and stable lithium metal batteries.