Clear distinction between the underdoped and overdoped regime in the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="italic">T</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="italic">c</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>suppression of Cu-site-substituted high-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="italic">T</mml:mi></mml:mrow><m

Kluge, Th.; Koike, Yasuhiro; Fujiwara, Akihiko; Kato, Masaru; Noji, Takashi; Saito, Yoshitami

doi:10.1103/physrevb.52.r727

Cited by 50 publications

(34 citation statements)

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“…For strong scatterers, these resonances lie close to the Fermi energy, and significantly modify bulk superconducting properties 5,6 . The local (atomic scale) effects of these resonances have been studied by several probes, such as nuclear magnetic resonance 7-11 (NMR) and muon spin relaxation (µSR) 12 .…”

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confidence: 95%

Visualization of the interplay between high-temperature superconductivity, the pseudogap and impurity resonances

et al. 2008

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In conventional superconductors, the superconducting gap in the electronic excitation spectrum prevents scattering of low-energy electrons. In high-temperature superconductors (HTSs), an extra gap, the pseudogap 1 , develops well above the superconducting transition temperature T C . Here, we present a new avenue of investigating the pseudogap state, using scanning tunnelling microscopy (STM) of resonances generated by single-atom scatterers. Previous studies on the superconducting state of HTSs 2 have led to a fairly consistent picture in which potential scatterers, such as Zn, strongly suppress superconductivity in an atomic-scale region, while generating low-energy excitations with a spatial distribution-as imaged by STM 3,4 -indicative of the d-wave nature of the superconducting gap. Surprisingly, we find that similar native impurity resonances coexist spatially with the superconducting gap at low temperatures and survive virtually unchanged on warming through T C . These findings demonstrate that properties of impurity resonances in HTSs are not determined by the nature of the superconducting state, as previously suggested, but instead provide new insights into the pseudogap state.In d-wave superconductors, such as the high-temperature superconductors (HTSs), impurities act as pair breakers, giving rise to virtual bound states, or resonances, within the gap. For strong scatterers, these resonances lie close to the Fermi energy, and significantly modify bulk superconducting properties 5,6 . The local (atomic scale) effects of these resonances have been studied by several probes, such as nuclear magnetic resonance 7-11 (NMR) and muon spin relaxation (µSR) 12 . A variety of scanning tunnelling microscopy (STM) studies of impurity resonances in HTSs have been reported, including studies of native (unidentified) impurities 13,14 , intentionally doped Zn and Ni impurities 3,4 and intentionally placed surface impurities 15 . All of these STM studies demonstrated that impurity resonances are associated with an enhanced local density of states inside the gap, close to the Fermi energy. All of these studies were also carried out on Bi 2 Sr 2 CaCu 2 O 8+x (Bi-2212) near 4 K, significantly below T C .Here, we report on temperature-dependent STM studies of native impurities in overdoped (T C = 15 K) Bi 2−y Pb y Sr 2 CuO 6+x (Bi-2201). In addition to enabling comparison to previous studies in Bi-2212, Bi-2201 has the benefit of having a relatively low T C , thus enabling us to study impurity resonances below and above T C without the resonance being obscured by thermal broadening.To carry out the temperature-dependent measurements discussed here we have constructed an ultrahigh-vacuum STM with the ability to track atomically resolved regions-here surrounding individual impurities-over a wide range of temperatures. We begin our study at low temperatures, using an experimental methodology similar to that used in previous STM impurity studies 3,4 . We search for impurity resonances by recording a spectral survey, in which d...

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confidence: 95%

Visualization of the interplay between high-temperature superconductivity, the pseudogap and impurity resonances

et al. 2008

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“…In this situation, it is a plausible understanding that the T c suppression by impurities is due to the effect of carrier localization in the underdoped regime of hole-doped superconductors, while it is due to the pair-breaking effect based on the Abrikosov-Gorkov theory 41 in the overdoped regime. 25 In hole-doped cuprate superconductors, in fact, the decrease in T c /T c0 , where T c0 is T c at y = 0, with increasing impurity-concentration in the optimally doped and overdoped regimes is smaller than that in the underdoped regime and is independent of the carrier concentration. To confirm this, the values of T c /T c0 were plotted as shown in Fig.…”

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confidence: 98%

Pairing Symmetry Studied from Impurity Effects in the Undoped Superconductor T′-La_1.8Eu_0.2CuO₄

et al. 2016

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We have investigated the effects of magnetic Ni and nonmagnetic Zn impurities on the superconductivity in undoped T'-La 1.8 Eu 0.2 CuO 4 (T'-LECO) with the Nd 2 CuO 4 -type structure, using the polycrystalline bulk samples, to clarify the pairing symmetry. It has been found that both suppression rates of the superconducting transition temperature T c by Ni and Zn impurities are nearly the same and are very similar to those in the optimally doped and overdoped regimes of hole-doped T-La 2−x Sr x CuO 4 with the K 2 NiF 4 -type structure. These results strongly suggest that the superconductivity in undoped T'-LECO is of the d-wave symmetry and is mediated by the spin fluctuation. * E-mail: tkawamata@teion.apph.tohoku.ac.jp J. Phys. Soc. Jpn. LETTERSIt has long been believed that the high-T c superconductivity appears through the hole and electron doping into the antiferromagnetic mother compound Ln 2 CuO 4 (Ln: lanthanide elements) with the K 2 NiF 4 -type (so-called T-type) and Nd 2 CuO 4 -type (so-called T'-type) structure, respectively. 1 In electron-doped T'-Ln 2−x Ce x CuO 4 , it has also been known that the reduction annealing of the as-grown samples to remove excess oxygen occupying the apical site just above Cu in the CuO 2 plane is necessary for the appearance of superconductivity at x 0.14. [2][3][4] Recently, in adequately reduced thin films of T'-Nd 2−x Ce x CuO 4 (T'-NCCO), however, superconductivity has been observed in a wide range of x and even in the undoped mother compound of x = 0. 5 Moreover, the superconductivity in undoped T'- The study of the effects of magnetic and nonmagnetic impurities on the superconductivity is useful to clarify the pairing symmetry of the superconductivity, because in a conventional s-wave superconductor, the SC transition temperature T c is suppressed by magnetic impurities more rapidly than by nonmagnetic impurities. In an unconventional superconductor with a sign-changing SC gap such as a d-wave superconductor, on the other hand, T c is rapidly suppressed by nonmagnetic impurities as well as by magnetic impurities. In fact, many studies of the impurity effect on T c have been carried out in high-T c cuprate superconductors. [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] In hole-doped T-La 2−x Sr x CuO 4 (T-LSCO), the suppression of T c by nonmagnetic Zn is comparable or even slightly larger than the suppression by magentic Ni. 16-19, 22, 23, 27, 28 Such a tendency has also been observed in hole-doped Bi-2212 25, 29 and YBa 2 Cu 3 O 7 , 21,22,27 leading to the conclusion that the pairing symmetry of hole-doped high-T c cuprate superconductors is unconventional d-wave mediated by spin fluctuation. In electron-doped T'-NCCO, on the other hand, the T c suppression by Ni is much more rapid than by Zn. 18,20,24,32 In the electron- 20,23,30 respectively. It is found that both suppression rates of T c in T'-LECO by the Ni and Zn substitution are nearly the same. Surprisingly, this behavior is different from that of electron-doped T'-NCCO with x = 0.15 in...

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“…Suppression of T c by impurities in overdoped systems does not depend on the doping level p, while in underdoped samples it is strongly doping-dependent [50]. Given that the pseudogap state occurs exactly at low doping, the observed p-dependence emphasizes the importance of the ground state in the response of the system to the disorder.…”

Section: Role Of Disorder In Cupratesmentioning

confidence: 88%

Impurities in multiband superconductors

Korshunov¹,

Togushova²,

Dolgov³

2016

Phys.-Usp.

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Abstract. Disorder Ð impurities and defects violating the ideal long-range order Ð is always present in solids. It can result in interesting and sometimes unexpected effects in multiband superconductors, especially if the superconductivity is unconventional, thus having symmetry other than the usual s-wave. This paper uses the examples of iron-based pnictides and chalcogenides to examine how both nonmagnetic and magnetic impurities affect superconducting states with s AE and s order parameters. We show that disorder causes the transition between s AE and s states and examine what observable effects this transition can produce.

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Clear distinction between the underdoped and overdoped regime in theTcsuppression of Cu-site-substituted high-T

Cited by 50 publications

References 3 publications

Visualization of the interplay between high-temperature superconductivity, the pseudogap and impurity resonances

Visualization of the interplay between high-temperature superconductivity, the pseudogap and impurity resonances

Pairing Symmetry Studied from Impurity Effects in the Undoped Superconductor T′-La_1.8Eu_0.2CuO₄

Impurities in multiband superconductors

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Clear distinction between the underdoped and overdoped regime in theTcsuppression of Cu-site-substituted high-T

Cited by 50 publications

References 3 publications

Visualization of the interplay between high-temperature superconductivity, the pseudogap and impurity resonances

Visualization of the interplay between high-temperature superconductivity, the pseudogap and impurity resonances

Pairing Symmetry Studied from Impurity Effects in the Undoped Superconductor T′-La1.8Eu0.2CuO4

Impurities in multiband superconductors

Contact Info

Product

Resources

About

Pairing Symmetry Studied from Impurity Effects in the Undoped Superconductor T′-La_1.8Eu_0.2CuO₄