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 R2Ir2O7 (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.

Quasiparticle interference (QPI) imaging of Bogoliubov excitations in quasi-two dimensional unconventional superconductors has become a powerful technique for measuring the superconducting gap and its symmetry. Here, we present the extension of this method to three-dimensional superconductors and analyze the expected QPI spectrum for the two-component heavy fermion superconductor UPt3 whose gap structure is still controversial. Starting from a 3D electronic structure and the three proposed chiral gap models E1g,u or E2u, we perform a slab calculation that determines the 2D continuum Bogoliubov-de Gennes (BdG) surface quasiparticle bands and in addition the in-gap flat-band Andreev bound states that lead to surface Weyl arcs connecting the projected gap nodes. Both features are very distinct for the three models, in particular the most prominent E2u candidate is singled out by the existence of two Weyl arcs due to the double monopole node points. The signature of these distinct surface bound and continuum states that is left in QPI is derived and discussed. We show that it provides a fingerprint that may finally determine the true nodal structure of UPt3 superconductor.PACS numbers: 74.20. Rp, 74.55.+v, 74.70.Tx, 03.65.vf The Cooper-pairing mechanism in many heavy-fermion superconductors (SCs) has not yet been identified. Partially this is connected to the fact that the superconducting gap symmetry, which encodes this mechanism,was not yet unambiguously determined in these compounds. Among various experimental techniques, Bogoliubov quasiparticle interference (QPI) as measured by the scanning tunneling spectroscopy imaging has become a notable technique for studying gaps of SCs, which possess strong quasi-two-dimensional electronic structure such as high-T c cuprates [1] and Fe-pnictides [2].However, if the quasiparticle energy has a significant dispersion along k z direction, the resulting Fermi surface (FS) also shows considerable corrugation along k z as it is for example the case in CeCoIn 5 . Then one could either use an effective artifical 2D FS model [3,4] or a model with corrugation and then integrate over the momentum perpendicular to the plane [5]. Both are ad-hoc methods that cannot be applied to fully 3D SCs like UPt 3 .The heavy fermion metal UPt 3 is the only known unconventional SC [6] with a two-component gap function. It must therefore belong to an E-type representation of its hexagonal D 6h symmetry group. The early thermodynamic evidence like two specific heat jumps [6][7][8] and two upper critical field curves [9-11] is reviewed in Refs. [12][13][14]. Finally a consensus emerged that the E 2u triplet f -wave gap function [15,16] rather than the originally proposed [17,18] singlet E 1g model is realized. Both model gap functions have similar nodal structure: A line node in the hexagonal ab symmetry plane and two point nodes at the poles on the k z -axis which are of first (E 1g ) or second (E 2u ) order. More recently as a result of thermal conductivity [19][20][21] and specific heat [22] m...