Fluctuation phase in a topological strongly correlated CoSi

Abstract

A thermodynamic fluctuation phase arising in the semi-metallic compound CoSi is considered. Its ground state electronic spectrum is characterized by intersection of the branches, in the energy region of which there is a strong Berry curvature. It is shown that a negative intermode coupling arises in a system of strongly correlated d-electrons, which leads to thermodynamic instability of the ground state of the Weyl semi-metal and to the appearance of electron density fluctuations. In this case, spatial regions of spin short-range order with fixed Berry phase differences are induced, which is chiral due to the Dzyaloshinsky-Moriya (DM) interaction. In an external magnetic field, due to the negativity of the intermode coupling, magnetization of the spin system takes place in the direction opposite to the field, which is accompanied by an increase in entropy. It was found that with decreasing temperature (due to a shift in the chemical potential), the intermode coupling disappears, the entropy abruptly decreases, which can be considered as a topological electronic transition (TET) into the Weyl semi-metallic phase.