Impurity-induced virtual bound states in<i>d</i>-wave superconductors

Balatsky, A. V.; Salkola, M. I.; Rosengren, Anders

doi:10.1103/physrevb.51.15547

Cited by 283 publications

(341 citation statements)

References 17 publications

(18 reference statements)

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“…30 Also in this one-impurity case we reproduce the constant-energy LDOS maps recently calculated by Wang and Lee. 31,32 Motivated by the qualitative agreement of the spin structure in Fig.…”

Section: Fig 2 ͑A͒mentioning

confidence: 60%

Checkerboard local density of states in striped domains pinned by vortices

Andersen

Hedegård²,

Bruus³

2003

Phys. Rev. B

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We discuss recent elastic neutron scattering and scanning tunneling experiments on High-Tc cuprates exposed to an applied magnetic field. Antiferromagnetic vortex cores operating as pinning centers for surrounding stripes is qualitatively consistent with the neutron data provided the stripes have the antiphase modulation. Within a Green's function formalism we study the low energy electronic structure around the vortices and find that besides the dispersive quantum interference there exists a non-dispersive checkerboard interference pattern consistent with recent scanning tunneling measurements. Thus both experiments can be explained from the physics of a single CuO2 plane.

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Section: Fig 2 ͑A͒mentioning

confidence: 60%

Checkerboard local density of states in striped domains pinned by vortices

Andersen

Hedegård²,

Bruus³

2003

Phys. Rev. B

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“…On the other hand, in such a picture one expects small current at the impurity site for negative tip bias due to the localized electron on the Zn, but enhanced current at nearest neighbor sites 10 . Empirically, the opposite is seen 5 , which has prompted a number of theoretical explanations.…”

Section: Introductionmentioning

confidence: 99%

“…The existence of impurity bound states of nonmagnetic type in unconventional superconductors was first discussed by Stamp 8 , while the use of STM to probe impurity wave functions in a d-wave superconductor was proposed by Byers et al 9 . Balatsky et al 10 then calculated the bound state wave function in the d-wave case appropriate to cuprate superconductors. All these calculations modeled the impurity as a simple point-like potential scatter.…”

Section: Introductionmentioning

confidence: 99%

Ab initiocalculation of impurity effects in copper oxide materials

2005

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We describe a method for calculating, within density functional theory, the electronic structure associated with typical defects which substitute for Cu in the CuO 2 planes of high-T c superconducting materials. The focus is primarily on Bi 2 Sr 2 CaCu 2 O 8 , the material on which most STM measurements of impurity resonances in the superconducting state have been performed. The magnitudes of the effective potentials found for Zn, Ni and vacancies on the in-plane Cu sites in this host material are remarkably consistent with phenomenological fits of potential scattering models to STM resonance energies. The effective potential ranges are quite short, of order 1 Å with weak long range tails, in contrast to some current models of extended potentials which attempt to fit STM data.For the case of Zn and Cu vacancies, the effective potentials are strongly repulsive, and states on the impurity site near the Fermi level are simply removed. The local density of states (LDOS) just above the impurity is nevertheless found to be a maximum in the case of Zn and a local minimum in case of the vacancy, in agreement with experiment. The Zn and Cu vacancy patterns are explained as due to the long-range tails of the effective impurity potential at the sample surface. The case of Ni is richer due to the Ni atom's strong hybridization with states near the Fermi level; in particular, the short range part of the potential is attractive, and the LDOS is found to vary rapidly with distance from the surface and from the impurity site. We propose that the current controversy surrounding the observed STM patterns can be resolved by properly accounting for the effective impurity potentials and wave-functions near the cuprate surface. Other aspects of the impurity states for all three species are discussed.2

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“…The impurity averaging method for unconventional superconductors has been explicitly questioned by some recent work [13]. The gap nodes lead to unusual wavefunctions for the bound states, with the possibility of anomalous overlaps between well-separated impurities.…”

Section: Introductionmentioning

confidence: 99%

Bound states and impurity averaging in unconventional superconductors

Joynt

1997

J Low Temp Phys

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The question of anomalous transport due to a band of impurity states in unconventional superconductors is discussed. In general, the bound state energies are not in midgap, even in the unitarity limit. This implies that, generically, the states associated with impurities are broad resonances, not true bound states. There is no impurity band in the usual sense of the phrase.The wavefunctions of these resonances possess interesting anisotropies in real space, but this does not result in anomalous hopping between impurities.I conclude that the system of resonances produces no qualitative modifications to the T-matrix theory with impurity averaging which is normally used to treat the low-temperature transport of unconventional superconductors.However, users of this method often assume a density of states which is symmetric around the chemical potential. This is not normally the case. It is found that the non-crossing approximation is not valid in a strictly twodimensional system.

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Impurity-induced virtual bound states ind-wave superconductors

Cited by 283 publications

References 17 publications

Checkerboard local density of states in striped domains pinned by vortices

Checkerboard local density of states in striped domains pinned by vortices

Ab initiocalculation of impurity effects in copper oxide materials

Bound states and impurity averaging in unconventional superconductors

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