Proximity-induced superconductivity in Weyl semimetals

Abstract

We study superconducting proximity effects in Weyl semimetals (WSM) with broken time-reversal symmetry by tunnel-coupling one of its surfaces to an s-wave superconductor using the Green's function approach. We find that the band structure develops coherence peaks, but despite the presence of metallic states in the bulk, the coherence peaks do not extend far into the bulk and remain confined to a few layers close to the interface, similar to the proximity effect in the topological insulators (TI) which are gapped in the bulk. The Weyl nodes remain unaffected, and in that sense, no true gap develops. We also study the induced pand s-wave pairing amplitudes classified by their symmetries, as a function of the various parameters of the theory, and note the exponential decay of the induced pairings in the bulk both in the TI and the WSM, even at finite chemical potential.

Dynamical density and spin response of Fermi arcs and their consequences for Weyl semimetals

“…Evidently, the two orbitals are of opposite parity. The Hamiltonian describes a weak TI for | | < 2|t|, a strong TI for 2|t| < | | < 6|t|, and a trivial insulator for 6|t| < | | [53,54]. In the following, we will consider the phase boundary between the topological and trivial insulator at = 6t with t > 0, where the bulk gap closes at k = 0 and Eq.…”

0−π transitions in a Josephson junction of an irradiated Weyl semimetal

“…We model the coupling with the superconductor by adding a self-energyΣ(ω) 15,22 to the first and last sites of the bare Green's function G R 0 .Σ accounts for tunnelling processes between the WSM and superconductor at the boundaries. The total retarded Green's function of the SWS device is…”

Weyl-Majorana solenoid

“…The parameters are the same as in figure 4, with periodic boundary conditions in the z-direction. 11 Figure 7 is for an NS junction with a single interface at positive and negative p =  k 120 y . Figures 2, 4, and 5 are for an SNS junction with two interfaces at a single p = k 120 y .…”

“…An interesting way to differentiate surface from bulk is to bring the Weyl semimetal into contact with a superconductor. While the Weyl cones in the bulk remain largely unaffected, the surface states acquire the mixed electron-hole character of a charge-neutral Bogoliubov quasiparticle-a Majorana fermion [8][9][10][11][12][13]. Here we investigate this proximity effect in the nanowire geometry of figure 1, in which an axial magnetization causes the surface modes to spiral along the wire, essentially forming a solenoid on the nanoscale [7].…”