Electron-momentum dependence of electron-phonon coupling underlies dramatic phonon renormalization in YNi2B2C

Electron-phonon coupling, i.e., the scattering of lattice vibrations by electrons and vice versa, is ubiquitous in solids and can lead to emergent ground states such as superconductivity and charge-density wave order. A broad spectral phonon line shape is often interpreted as a marker of strong electron-phonon coupling associated with Fermi surface nesting, i.e., parallel sections of the Fermi surface connected by the phonon momentum. Alternatively broad phonons are known to arise from strong atomic lattice anharmonicity. Here, we show that strong phonon broadening can occur in the absence of both Fermi surface nesting and lattice anharmonicity, if electron-phonon coupling is strongly enhanced for specific values of electron-momentum, k. We use inelastic neutron scattering, soft x-ray angle-resolved photoemission spectroscopy measurements and ab-initio lattice dynamical and electronic band structure calculations to demonstrate this scenario in the highly anisotropic tetragonal electron-phonon superconductor YNi2B2C. This new scenario likely applies to a wide range of compounds.

A new understanding of the origin of electric current

Because charge, current, resistance, and voltage are understood based on the perspective of electricity, they can describe various electrical phenomena well, but they cannot explain their origins. Therefore, this article attempts to propose a new understanding of these phenomena from the perspective of mechanics to obtain a feasible way of explaining their origin and to solve problems that cannot be explained from the perspective of electricity. Specifically, this paper attempts to explain the origin of electric charge to obtain a new understanding of the origin of current and to obtain a new understanding of voltage and resistance by explaining the origin of current. Finally, from the perspective of mechanics, the origin of charge can be understood as a manifestation of electron momentum, the origin of current can be understood as a momentum flow, the origin of resistance can be understood as a momentum resistance, and the origin of voltage can be understood as a potential pressure (potential difference) of electron orbital potential. This new understanding of the origin of current from a mechanical perspective can provide a new theoretical explanation for high-temperature superconductivity.