Ideal quadratic fermionic point state with multiple band degeneracy

Abstract

As the study of topological states witnessed rapid progress and fast development, the current research has been expanded from conventional linear dispersion into high order conditions. In comparison with the linear type, high order topological elements feature multiple exotic properties, such as large topological charge, peculiar Berry phase, and chiral surface states, which could lead to the finding of other new physics. In this study, we present a realistic material candidate hosting an ideal quadratic fermionic point state with multiple band degeneracy. Based on first principles calculation and effective model argument, the origin of the quadratic order is analyzed, and its dispersion conditions are examined. Due to the clean band structure, prominent surface states are observed and they exhibit both large energy variation and broad spatial distribution. These beneficial features are very advantageous for future experimental investigations. This work can significantly enhance the research on high order topological states and, in particular, the proposed material can provide an effective platform for quadratic fermionic point states.