Lecturer: Dr. Haim Beidenkopf
Affiliation: Weizmann Institute of Science
Abstract:
A defining property of a topological material is
the existence of surface bands that cannot be
realized but as the termination of a topological
bulk. In a Weyl semi-metal these are given by
the surface Fermi-arcs, whose open-contour
Fermi-surface curves between pairs of surface
projections of bulk Weyl points of opposite
chirality. We show first scanning tunneling
spectroscopic visualization of these Fermi arc
states on the surface of the recently discovered
Weyl semi-metal tantalum arsenide (TaAs). Its
surface hosts 12 Fermi arcs alongside several
surface bands of non-topological origin. Using
the distinct structure and spatial distribution of
the wave functions associated with the
different bands we detect all possible scattering
processes in which Fermi arcs are involved
(intra- and inter arc and arc-trivial). Each of
these imaged scattering processes entails
information on the unique nature of Fermi arcs
in TaAs: their contour, their dispersion and its
relation with the Weyl points, the relative
uniform structure of their Bloch wave function,
and their association with tantalum sites which
indicates their close relation with the tantalum
derived bulk Weyl cones. The analysis technique
we demonstrate, based on the structure of the
Bloch wave function within the unit cell, is
applicable to other electronic systems of
interest such as high temperature
superconductors and topological crystalline
insulators.