Impact of topology on the impurity effects in extendeds-wave superconductors with spin-orbit coupling

Abstract

We investigate the impact of topology on the existence of impurity subgap states in a time-reversal-invariant superconductor with an extended s-wave pairing and strong spin-orbit coupling. By simply tuning the chemical potential we access three distinct phases: topologically trivial s-wave, topologically non-trivial s±-wave, and nodal superconducting phase. For a single potential impurity we find subgap impurity bound states in the topological phase, but notably no subgap states in the trivial phase. This is in sharp contrast with the expectation that there would be no subgap state in the presence of potential impurities in s-wave superconductors. These subgap impurity states have always finite energies for any strength of the potential scattering and subsequently, the superconducting gap in the topological s±-wave phase survives but is attenuated in the presence of finite disorder. By creating islands of potential impurities we smoothly connect the single impurity results to topological edge states of impurity island. On the other hand, magnetic impurities lead to the formation of Yu-Shiba-Rusinov states in both the trivial and topological phases, which even reach zero energy at certain scattering strengths. We thus propose that potential impurities can be a very valuable tool to detect time-reversal-invariant topological superconductivity.

Spin-orbit coupling induced splitting of Yu-Shiba-Rusinov states in antiferromagnetic dimers

“…All of these experimental observations have been explained based on the theoretical framework formulated by Yu, Shiba, and Rusinov 15 – 17 . This theory does not take into account SOC, and its influence on the Shiba states has been considered in surprisingly few works so far 34 , 35 . Over the recent decades, a plethora of novel phenomena in solid-state physics has been demonstrated to arise due to the combination of SOC with inversion-symmetry breaking.…”

Entangled end states with fractionalized spin projection in a time-reversal-invariant topological superconducting wire

“…[11][12][13][14][15][16][17][18][19][20] This property has interesting implications which can be relevant for their detection and manipulation. [21][22][23][24][25][26] For a recent review on proposals to realize the TRITOPS phase, see Ref. 27.…”

Quasiparticle focusing of bound states in two-dimensional $s$-wave superconductors

“…In the limit α = 1 this pairing function is known under the name of extended s-wave or unconventional s ± -wave and it has been proposed as a candidate to describe ironbased superconductors [59,60]. However, we choose α = 0 in our calculations to maximize the variation of the gap along the Fermi contour, thereby enhancing the effect of the pairing function anisotropy on the LDOS of the YSR state.…”