Interplay of magnetism and high-Tc superconductivity at individual Ni impurity atoms in Bi2Sr2CaCu2O8+δ

Hudson, Eric; Lang, K. M.; Madhavan, Vidya; Pan, S. H.; Eisaki, H.; Uchida, S.; Davis, J. C.

doi:10.1038/35082019

Cited by 331 publications

(330 citation statements)

References 31 publications

(44 reference statements)

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“…Insets show dI/dV maps on top of a Ni impurity. 43 Se vacancy (Fig. 5b) induce an asymmetric, sub-gap resonance at small negative bias.…”

Section: Single Atom Defects As Local Probesmentioning

confidence: 98%

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Interplay of chemical disorder and electronic inhomogeneity in unconventional superconductors

Zeljkovic

Hoffman

2013

Phys. Chem. Chem. Phys.

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Many of today's forefront materials, such as high-T c superconductors, doped semiconductors, and colossal magnetoresistance materials, are structurally, chemically and/or electronically inhomogeneous at the nanoscale. Although inhomogeneity can degrade the utility of some materials, defects can also be advantageous. Quite generally, defects can serve as nanoscale probes and facilitate quasiparticle scattering used to extract otherwise inaccessible electronic properties. In superconductors, nonstoichiometric dopants are typically necessary to achieve a high transition temperature, while both structural and chemical defects are used to pin vortices and increase critical current. Scanning tunneling microscopy (STM) has proven to be an ideal technique for studying these processes at the atomic scale.In this perspective, we present an overview of STM studies on chemical disorder in unconventional superconductors, and discuss how dopants, impurities and adatoms may be used to probe, pin or enhance the intrinsic electronic properties of these materials.

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“…Insets show dI/dV maps on top of a Ni impurity. 43 Se vacancy (Fig. 5b) induce an asymmetric, sub-gap resonance at small negative bias.…”

Section: Single Atom Defects As Local Probesmentioning

confidence: 98%

“…43 Ni atoms are magnetic, and thought to be in the Ni 2+ 3d 8 electronic state with spin S = 1, as compared to spin S = 1 2 for Cu atoms. In dI/dV images, Ni resonances are observed as ''cross-shaped'' features at +9 meV and as ''X-shaped'' features at À9 meV (inset in Fig.…”

Section: Single Atom Defects As Local Probesmentioning

confidence: 99%

Interplay of chemical disorder and electronic inhomogeneity in unconventional superconductors

Zeljkovic

Hoffman

2013

Phys. Chem. Chem. Phys.

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“…As various different theoretical proposals for the pseudo-gap have been put forward the need of experimental probes that are able to distinguish between them is of great interest. Here we argue that scanning tunneling microscopy (STM) experiments in underdoped HTSC, that serve as a local probe of impurity states [4,5], can be used in order to differentiate between at least two classes of proposals.In one class of models the pseudo-gap is ascribed to a precursor pairing amplitude whose phase coherence is destroyed above T c [6,7]. Since such a state exhibits off-diagonal short-range order, particle and hole states get mixed and consequently an induced impurity state is composed of both a particle and a hole-like component.…”

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confidence: 99%

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confidence: 99%

Distinguishing models for the pseudo-gap in cuprate superconductors by probing the spatial distribution of impurity states

Kübert¹

2003

Braz. J. Phys.

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We argue that the spatial distribution of resonant impurity states in underdoped high-Tc superconductors serves as a probe for distinguishing different theoretical models for the pseudogap state. Superconducting pairing fluctuations are characterized by off-diagonal short-range order which distinguishes them from other possible instabilities that could give rise to the pseudogap phenomena. Due to the mixture of particle and hole states in a superconductor an impurity resonant state is composed of both a particle and a hole-like component. On the contrary a state with a gap induced by a particle-hole instability, like a d-density wave (DDW) or spin-density wave (SDW), exhibits no off-diagonal short-range order and consequently a resonant impurity state consists of only one either particle or hole-like component. Furthermore, a charge-spin separated state shows no resonance state at all inside the gap region.One of the most intriguing property of the underdoped high-temperature superconductors (HTSC) is the suppression of single-particle weight around the Fermi energy [1, 2, 3] for temperatures well above T c . As a consequence the electronic behavior of these materials deviates substantially from that of conventional superconductors. The origin of this so-called pseudo-gap state is one of the key problems to be solved in order to understand the underlying microscopic mechanism of the phenomena of HTSC. As various different theoretical proposals for the pseudo-gap have been put forward the need of experimental probes that are able to distinguish between them is of great interest. Here we argue that scanning tunneling microscopy (STM) experiments in underdoped HTSC, that serve as a local probe of impurity states [4,5], can be used in order to differentiate between at least two classes of proposals.In one class of models the pseudo-gap is ascribed to a precursor pairing amplitude whose phase coherence is destroyed above T c [6,7]. Since such a state exhibits off-diagonal short-range order, particle and hole states get mixed and consequently an induced impurity state is composed of both a particle and a hole-like component. On the other hand in models where the origin of the pseudo-gap is due to a different type of instability (DDW, SDW, stripe order etc.) the property of particle and hole mixing is absent and thus an impurity state has only one either particle or hole-like component. This difference in the local electronic density of states (LDOS) around an impurity can be measured by scanning tunneling microscopy. This prediction can be readily used by STM experiments to detecd for the DDW state in the underdoped cuprates.The local differential conductance measured at bias voltage V by STM is proportional to the local electron density of states. Here we study the LDOS around a magnetic or non-magnetic (U = 0) impurity in a system with competing d-wave superconducting (DSC) and DDW order. The model Hamiltonian is given by (Q = (π, π))where k = 2t (cos k x ) + cos k y ) − 4t (cos k x cos k y ) − µ is the dispersion o...

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“…This is mainly due to the large experimental progress in low temperature scanning tunneling microscopy (STM). In particular, STM measurements have provided detailed local density of states (LDOS) images around single nonmagnetic [3,4] (Zn) and magnetic [5] (Ni) impurities on the surface of the high temperature superconductor Bi 2 Sr 2 CaCuO 4+δ (BSCCO). More recently the energy dependence of the Fourier transformed LDOS images was measured in the superconducting state of optimally doped BSCCO [6].…”

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confidence: 99%

Impurity resonances and the origin of the pseudo-gap

Andersen¹

2003

Braz. J. Phys.

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We study the structure of resonance states localized around nonmagnetic impurities in the CuO 2 planes of the cuprate superconductors within a potential scattering formalism. In particular we show that strong quantum interference effects arise between several impurities. This interference can be utilized to distinguish the dwave superconducting state from the phase with d-density wave order. This is important if the origin of the pseudo-gap state in the underdoped regime of the High Tc superconductors is caused by preformed Cooper pairs or staggered orbital currents. Furthermore impurity interference can be utilized to reveal subdominant superconducting order parameters and to pose further constraints on the potential scattering scenario.For conventional superconductors Yu and Shiba[1] first showed that as a result of the interaction between a magnetic impurity and the spin density of the conduction electrons, a bound state located around the magnetic impurity is formed inside the gap in the strong-scattering (unitary) limit. For anisotropic superconductors a number of authors generalized the Yu-Shiba approach to study the effects of single impurities [2].Many important questions concerning the electronic structure of the High T c materials still need to be answered. The study of single impurity effects provide a promising path to yield some answers. This is mainly due to the large experimental progress in low temperature scanning tunneling microscopy (STM). In particular, STM measurements have provided detailed local density of states (LDOS) images around single nonmagnetic [3,4] (Zn) and magnetic [5] (Ni) impurities on the surface of the high temperature superconductor Bi 2 Sr 2 CaCuO 4+δ (BSCCO). More recently the energy dependence of the Fourier transformed LDOS images was measured in the superconducting state of optimally doped BSCCO[6]. The dispersive features were explained by elastic quasi-particle interference resulting from a single weak, nonmagnetic impurity [7]. This gives credence that a scattering potential picture can yield valuable predictions in the superconducting state of these materials. Furthermore, it was recently shown by Martin et al. [8] that both the energetics of the resonance state and its spatial dependence around a strong potential scatterer (e.g. Zn) can be accounted for by including the tunnelling (the filter) through excited states from the CuO 2 planes to the top BiO layer probed by the STM tip. In order to obtain agreement with the measured LDOS one needs to attribute a large negative potential to the Zn site in agreement with the filled d shell of this atom; the potential will strongly repel holes, i.e. attract the electrons.Experimentally there is also evidence from NMR measurements that magnetic moments are induced around nonmagnetic impurities [9]. In this paper we assume, however, that the large potential scattering off the impurity site itself is dominating the final LDOS.Future experimental ability to control the position of the impurities on the surface of a superconduc...

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Interplay of magnetism and high-Tc superconductivity at individual Ni impurity atoms in Bi2Sr2CaCu2O8+δ

Cited by 331 publications

References 31 publications

Interplay of chemical disorder and electronic inhomogeneity in unconventional superconductors

Interplay of chemical disorder and electronic inhomogeneity in unconventional superconductors

Distinguishing models for the pseudo-gap in cuprate superconductors by probing the spatial distribution of impurity states

Impurity resonances and the origin of the pseudo-gap

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