Impurity-induced states in conventional and unconventional superconductors

By Alexander V. Balatsky, I. Vekhter, Jian-Xin Zhu. 2004

878 citations recorded by the source corpus.

We review recent developments in our understanding of how impurities influence the electronic states in the bulk of superconductors. Our focus is on the quasi-localized states in the vicinity of impurity sites in conventional and unconventional superconductors and our goal is to provide a unified framework for their description. The non-magnetic impurity resonances in unconventional superconductors are directly related to the Yu-Shiba-Rusinov states around magnetic impurities in conventional s-wave systems. We review the physics behind these states, including quantum phase transition between screened and unscreened impurity, and emphasize recent work on d-wave superconductors. The bound states are most spectacularly seen in scanning tunneling spectroscopy measurements on high-$T_c$ cuprates, which we describe in detail. We also discuss very recent progress on the states coupled to impurity sites which have their own dynamics, and impurity resonances in the presence of an order competing with superconductivity. Last part of the review is devoted to influence of local deviations of the impurity concentration from its average value on the density of states in s-wave superconductors. We review how these fluctuations affect the density of states and show that s-wave superconductors are, strictly speaking, gapless in the presence of an arbitrarily small concentration of magnetic impurities.

Subfields: Condensed Matter Physics

View Paper: https://www.semanticscholar.org/paper/5833c3cd692caa350c62348be27e78d88beef251

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In Condensed Matter Physics

Citations in the corpus

The electronic properties of graphene (2007, result): “The latter has been extensively studied in relation to the effects of impurities on the electronic structure of d-wave superconductors (Balatsky et al., 2006), and numerical results are in agreement with the existence of this solution.”
Defects in correlated metals and superconductors (2007, methodology): “It was argued in (Balatsky et al., 2006), where the controversy is reviewed in much more detail, that models of this kind require unphysically small nonmagnetic compared to magnetic interactions to explain STM spectra.”
Numerical renormalization group method for quantum impurity systems (2007, background): “Let us now consider magnetic impurities in superconducting hosts (for a general review on impurity effects in conventional and unconventional superconductors, see Balatsky et al. (2006)).”
Plain s-wave superconductivity in single-layer FeSe on SrTiO3 probed by scanning tunnelling microscopy (2015, background): “To further determine the pairing symmetry, we probed impurity-induced effects [20-22].”
Coherent long-range magnetic bound states in a superconductor (2015, background): “Rusinov suggested that around magnetic atoms the decaying YSR wavefunction should have a spatially oscillating structure [12, 15, 16].”