Quasiparticle interference from different impurities on the surface of pyrochlore iridates: signatures of the Weyl phase

TL;DR

This paper investigates quasiparticle interference patterns on the surface of pyrochlore iridates in the Weyl phase, revealing signatures of topological surface states and impurity effects using a multi-band Hubbard model.

Contribution

It introduces a detailed analysis of QPI patterns in pyrochlore iridates' Weyl phase, highlighting impurity effects and surface state textures with exact diagonalization.

Findings

QPI patterns reveal spin and orbital textures of surface states

Absence of certain backscattering processes indicates topological protection

Additional features in QPI patterns distinguish Weyl phase in pyrochlore iridates

Abstract

Weyl semimetals are gapless three-dimensional topological materials where two bands touch at an even number of points in the bulk Brillouin zone. These semimetals exhibit topologically protected surface Fermi arcs, which pairwise connect the projected bulk band touchings in the surface Brillouin zone. Here, we analyze the quasiparticle interference patterns of the Weyl phase when time-reversal symmetry is explicitly broken. We use a multi-band $d$-electron Hubbard Hamiltonian on a pyrochlore lattice, relevant for the pyrochlore iridate R$_2$Ir$_2$O$_7$ (where R is a rare earth). Using exact diagonalization, we compute the surface spectrum and quasiparticle interference (QPI) patterns for various surface terminations and impurities. We show that the spin and orbital texture of the surface states can be inferred from the absence of certain backscattering processes and from the symmetries of the QPI features for non-magnetic and magnetic impurities. Furthermore, we show that the QPI patterns of the Weyl phase in pyrochlore iridates may exhibit additional interesting features that go beyond those found previously in TaAs.