Zero-mass particles "Dillac electrons" exist in a two-dimensional region such as graphene (an atomic layer material made by thinning graphite to a thickness of one atom).Graphene's Dirac electron has a mobility more than 2 times that of silicon, and exhibits high electrical and thermal conductivity.
Particles with zero mass in three-dimensional space, which are said to have a wider range of applications, are called "Weil particles", which are similar to Dirac electrons but essentially different.Weil particles have topological properties, and two types of particles with different "right-handed" and "left-handed" (chirality) are expressed in pairs, and the mass is zero unless they collide with each other. There is.
Recently, a new substance "Weyl semimetal" containing these Weyl particles has been theoretically proposed, and its material synthesis and experimental verification of Weyl particles have been strongly awaited.

This time, the joint research group succeeded in growing high-quality large single crystals of NbP (Nb: niobium, P: phosphorus).Focusing on the crystal structure, the electronic states of the Nb surface and the P surface were examined by angle-resolved photoelectron spectroscopy.As a result, it was clarified that the "Fermi arc" (the shape of the arc that the "open" Fermi surface takes in two dimensions) that characterizes the Weyl semimetal has a completely different electronic state on each surface.
Furthermore, by superimposing two Fermi arcs, it was found that the intersection corresponds to the position of Weil particles in the solid.As a result, it was experimentally established that NbP is a new type of Weyl semimetal.

Since Weil particles have extremely high electrical and thermal conductivity, it is said that the development of next-generation devices with low power consumption and ultra-high-speed electrons will gain momentum in the future.