TY - JOUR

T1 - Density of states in gapped superconductors with pairing-potential impurities

AU - Bespalov, Anton

AU - Houzet, Manuel

AU - Meyer, Julia S.

AU - Nazarov, Yuli V.

PY - 2016/3/21

Y1 - 2016/3/21

N2 - We study the density of states in disordered s-wave superconductors with a small gap anisotropy. We consider disorder in the form of common nonmagnetic scatterers and pairing-potential impurities, which interact with electrons via an electric potential and a local distortion of the superconducting gap. Using quasiclassical Green functions, we determine the bound-state spectrum at a single impurity and the density of states at a finite concentration of impurities. We show that, if the gap is isotropic, an isolated impurity with suppressed pairing supports an infinite number of Andreev states. With growing impurity concentration, the energy-dependent density of states evolves from a sharp gap edge with an impurity band below it to a smeared BCS singularity in the so-called universal limit. Within one spin sector, pairing-potential impurities and weak spin-polarized magnetic impurities have essentially the same effect on the density of states. We note that, if a gap anisotropy is present, the density of states becomes sensitive to ordinary potential disorder, and the existence of Andreev states localized at pairing-potential impurities requires special conditions. An unusual feature related to the anisotropy is a nonmonotonic dependence of the gap edge smearing on impurity concentration.

AB - We study the density of states in disordered s-wave superconductors with a small gap anisotropy. We consider disorder in the form of common nonmagnetic scatterers and pairing-potential impurities, which interact with electrons via an electric potential and a local distortion of the superconducting gap. Using quasiclassical Green functions, we determine the bound-state spectrum at a single impurity and the density of states at a finite concentration of impurities. We show that, if the gap is isotropic, an isolated impurity with suppressed pairing supports an infinite number of Andreev states. With growing impurity concentration, the energy-dependent density of states evolves from a sharp gap edge with an impurity band below it to a smeared BCS singularity in the so-called universal limit. Within one spin sector, pairing-potential impurities and weak spin-polarized magnetic impurities have essentially the same effect on the density of states. We note that, if a gap anisotropy is present, the density of states becomes sensitive to ordinary potential disorder, and the existence of Andreev states localized at pairing-potential impurities requires special conditions. An unusual feature related to the anisotropy is a nonmonotonic dependence of the gap edge smearing on impurity concentration.

UR - http://resolver.tudelft.nl/uuid:8cea7557-81b3-43d0-a77f-1a44c4ce60d5

UR - http://www.scopus.com/inward/record.url?scp=84961875139&partnerID=8YFLogxK

U2 - 10.1103/PhysRevB.93.104521

DO - 10.1103/PhysRevB.93.104521

M3 - Article

AN - SCOPUS:84961875139

VL - 93

SP - 1

EP - 17

JO - Physical Review B (Condensed Matter and Materials Physics)

JF - Physical Review B (Condensed Matter and Materials Physics)

SN - 1098-0121

IS - 10

M1 - 104521

ER -