983 research outputs found
Multivalued current-phase relationship in a.c. Josephson effect for a three-dimensional Weyl semimetal WTe
We experimentally study electron transport between two superconducting indium
leads, coupled to a single WTe crystal, which is a three-dimensional Weyl
semimetal. We demonstrate Josephson current in long 5~m In-WTe-In
junctions, as confirmed by the observation of integer (1,2,3) and fractional
(1/3, 1/2, 2/3) Shapiro steps under microwave irradiation. Demonstration of
fractional a.c. Josephson effect indicates multivalued character of the
current-phase relationship, which we connect with Weyl topological surface
states contribution to Josephson current. In contrast to topological insulators
and Dirac semimetals, we do not observe periodicity in a.c. Josephson
effect for WTe at different frequencies and power, which might reflect
chiral character of the Fermi arc surface states in Weyl semimetal.Comment: the text is seriously corrected. arXiv admin note: text overlap with
arXiv:1801.0955
Conductance oscillations and zero-bias anomaly in a single superconducting junction to a three-dimensional topological insulator
We experimentally investigate Andreev transport through a single junction
between an s-wave indium superconductor and a thick film of a three-dimensional
topological insulator. We study samples with different
bulk and surface characteristics, where the presence of a topological surface
state is confirmed by direct ARPES measurements. All the junctions demonstrate
Andreev transport within the superconducting gap. For junctions with
transparent interfaces we find a number of nearly periodic
conductance oscillations, which are accompanied by zero-bias conductance
anomaly. Both effects disappear above the superconducting transition or for
resistive junctions. We propose a consistent interpretation of both effects as
originating from proximity-induced superconducting correlations within the
topological surface state
Signature of Fermi arc surface states in Andreev reflection at the WTe Weyl semimetal surface
We experimentally investigate charge transport through the interface between
a niobium superconductor and a three-dimensional WTe Weyl semimetal. In
addition to classical Andreev reflection, we observe sharp non-periodic subgap
resistance resonances. From an analysis of their positions, magnetic field and
temperature dependencies, we can interpret them as an analog of Tomasch
oscillations for transport along the topological surface state across the
region of proximity-induced superconductivity at the Nb-WTe interface.
Observation of distinct geometrical resonances implies a specific transmission
direction for carriers, which is a hallmark of the Fermi arc surface states.Comment: 5 pages, some misprints has been correcte
- …