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

Abstract

A magnetic impurity on a superconducting substrate induces in-gap Yu-Shiba-Rusinov (YSR) bound states, whose intricate spatial structure crucially influences the possibilities of engineering collective impurity states. By means of a saddle-point approximation we study the scattering processes giving rise to YSR states in gapped, two-dimensional superconductors. Further, we develop a theory which relates through a simple analytical expression an arbitrary energy dispersion of normal electrons in a two-dimensional host to the spatial features of the YSR states. Namely, we find that flatter segments of the Fermi surface with large Fermi velocity enhance the local density of states (LDOS) around the impurity. Our analytical approximation is quantitatively accurate against tight-binding calculations on various lattices with different Fermi surfaces, and it allows to predict the shape and orientation of YSR states observed in scanning tunneling spectroscopy experiments. We illustrate our results with a model of ${\mathrm{NbSe}}_2$.

14 pages, 5 figures

References in corpus (11)

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Cited by in corpus (8)

• Impurity-induced Friedel oscillations in altermagnets and $p$-wave magnets
• Wave-function engineering on superconducting substrates: Chiral Yu-Shiba-Rusinov molecules
• Bound states around impurities in a superconducting bilayer
• Tunneling spectra of impurity states in unconventional superconductors
• Diluted Yu-Shiba-Rusinov arrays on the $\beta$-Bi${}_2$Pd anisotropic superconductor
• Robust Spin Polarization of Yu-Shiba-Rusinov States in Superconductor/Ferromagnetic Insulator Heterostructures
• Anisotropy of Yu-Shiba-Rusinov states in NbSe${}_2$
• Detecting the topological winding of superconducting nodes via Local Density of States