Tunable Dirac Semimetals with Higher-order Fermi Arcs in Kagome Lattices Pd$_3$Pb$_2$X$_2$ (X = S, Se)

TL;DR

This paper predicts a new class of Dirac semimetals in kagome lattices that lack surface Fermi arcs but feature higher-order Fermi arcs and fractional hinge charges, with tunable phase transitions.

Contribution

It introduces Pd$_3$Pb$_2$X$_2$ kagome lattice materials as unique type-I DSMs with higher-order topological features, distinct from known DSMs.

Findings

Presence of higher-order Fermi arcs in Pd$_3$Pb$_2$X$_2$

Topological phase boundaries tunable by strain

Existence of fractional corner charges on hinges

Abstract

Bulk-boundary correspondence has achieved a great success in the identification of topological states. However, this elegant strategy doesn't apply to the Dirac semimetals (DSMs). Here, we propose that kagome lattices Pd$_3$Pb$_2$X$_2$ (X = S, Se) are unique type-I DSMs without surface Fermi arc states, which are different from the previous well-known DSMs, such as Na$_3$Bi and Cd$_3$As$_2$. Pd$_3$Pb$_2$X$_2$ are characterized by nontrivial topological invariant Z$_3$, guaranteeing a higher-order bulk-hinge correspondence and the existence of higher-order Fermi arcs, as well as fractional corner charges on the hinges. The type-I DSMs are located at the phase boundaries of several topological phases, including type-II DSMs and three-dimensional weak topological insulators. The phase transitions can be easily manipulated by external strain. Our results provide feasible platforms for the study of these unique DSMs and the related phase transitions.