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Chien, T. R.; Datars, W. R.; Lan, M. D.; Liu, J. Z.; Shelton, R.N.

doi:10.1103/physrevb.49.1342

Cited by 19 publications

(5 citation statements)

References 20 publications

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“…As shown in Fig.1 for La 2−x Sr x CuO 4 the effective mass anisotropy, measured in terms of γ = M c /M ab increases drastically by approaching the underdoped limit. This property, also observed in HgBa 2 CuO 4+δ [20] and YBa 2 Cu 3 O 7−x [22], appears to be generic and reveals the crossover from three (3D) to two dimensional (2D) behavior.…”

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confidence: 54%

“…In La 2−x Sr x CuO 4 , HgBa 2 CuO 4+x [19,20] and Bi 2 Sr 2 CuO 6+x [21]both, the underdoped and overdoped limits, corresponding to critical endpoints, are experimentally accessible. In other cuprates, including Bi 2 Sr 2 CaCu 2 O 8+x [21], YBa 2 Cu 3 O 7−x [22] and Y 1−x Pr x Ba 2 Cu 3 O 7−δ [23], only the underdoped and optimally doped regimes appear to be accessible. As shown in Fig.…”

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confidence: 99%

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Isotope Effects in Underdoped Cuprate Superconductors: A Quantum Critical Phenomenon

Schneider

Keller

2001

Phys. Rev. Lett.

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We show that the unusual doping dependence of the isotope effects on transition temperature and zero temperature in -plane penetration depth naturally follows from the doping driven 3D-2D crossover, the 2D quantum superconductor to insulator transition (QSI) in the underdoped limit and the change of the relative doping concentration upon isotope substitution. Close to the QSI transition both, the isotope coefficient of transition temperature and penetration depth approach the coefficient of the relative dopant concentration, and its divergence sets the scale. These predictions are fully consistent with the experimental data and imply that close to the underdoped limit the unusual isotope effect on transition temperature and penetration depth uncovers critical phenomena associated with the quantum superconductor to insulator transition in two dimensions. PACS numbers: 74.20. Mn, 74.25Dw, The observation of an unusual isotope effect in underdoped cuprate superconductors on transition temperature [1][2][3] and zero temperature penetration depth [4][5][6][7] poses a challenge to the understanding of high temperature superconductivity. In this letter we show that this behavior naturally follows from the doping driven 3D-2D crossover, the 2D superconductor to insulator (QSI) transition in the underdoped limit and the change of the relative doping concentration upon isotope substitution. Thus, the unusual isotope effect on superconducting properties of underdoped cuprates is derived to be a quantum critical phenomenon driven by variation of the dopant concentration.Consider [23], only the underdoped and optimally doped regimes appear to be accessible. As shown in Fig.1 for La 2−x Sr x CuO 4 the effective mass anisotropy, measured in terms of γ = M c /M ab increases drastically by approaching the underdoped limit. This property, also observed in HgBa 2 CuO 4+δ [20] and YBa 2 Cu 3 O 7−x [22], appears to be generic and reveals the crossover from three (3D) to two dimensional (2D) behavior.In our considerations the starting point is the critical endpoint of the phase transition line T c (x), where at T = 0 and x = x u , driven by variation of the dopant concentration x, the QSI transition occurs. Close to this critical endpoint the bulk superconductors correspond to a stack of independent superconducting slabs of thickness d s . Moreover, close to such a critical point, low energy properties depend only on the spatial dimensionality of the system, the number of components of the order parameter and the range of the interaction. The theory of quantum critical phenomena predicts that the transition temperature and zero temperature in -plane penetration depth scale as [24,17,18] z is the dynamic critical exponent, ν the exponent of the diverging length, a and b nonuniversal critical amplitudes, andmeasures the distance from the quantum critical point at x u , where in cuprate superconductors the QSI transition occurs. For a complex scalar order parameter and in D=2 the critical amplitudes a and b and the slab thickness d s ...

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confidence: 54%

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Isotope Effects in Underdoped Cuprate Superconductors: A Quantum Critical Phenomenon

Schneider

Keller

2001

Phys. Rev. Lett.

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“…For example, the room-temperature ratio of out-ofplane to in-plane resistivities ( c / ab ) is about 30-100 for YBCO, and 10 5 for Bi-2212 (Poole et al, 1995;Ong et al, 1996). In the superconducting state, large anisotropy in the magnetic penetration depths ( ab / c ) and the superconducting coherence length ( ab / c ) is also observed (Jannossy et al, 1990;Chien et al, 1994). The observation of strong anisotropy in resistivity, penetration depth, and other physical properties does not necessarily determine whether the high-T c superconductors are truly two-dimensional or merely anisotropic threedimensional electronic systems (Hussey et al, 1996).…”

Section: Cu-o Square/rectangular Latticementioning

confidence: 99%

Pairing symmetry in cuprate superconductors

2000

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Pairing symmetry in the cuprate superconductors is an important and controversial topic. The recent development of phase-sensitive tests, combined with the refinement of several other symmetry-sensitive techniques, has for the most part settled this controversy in favor of predominantly d-wave symmetry for a number of optimally hole-and electron-doped cuprates. This paper begins by reviewing the concepts of the order parameter, symmetry breaking, and symmetry classification in the context of the cuprates. After a brief survey of some of the key non-phase-sensitive tests of pairing symmetry, the authors extensively review the phase-sensitive methods, which use the half-integer flux-quantum effect as an unambiguous signature for d-wave pairing symmetry. A number of related symmetry-sensitive experiments are described. The paper concludes with a brief discussion of the implications, both fundamental and applied, of the predominantly d-wave pairing symmetry in the cuprates. CONTENTS I. Introduction 969 A. Evidence for Cooper pairing in cuprates 969 B. Order parameter in superconductors 970 C. Broken symmetry and symmetry classification of the superconducting state 971 1. Tetragonal crystal lattice 972 2. Orthorhombic crystal lattice 973 3. Cu-O square/rectangular lattice 973 II. Non-Phase-Sensitive Techniques 974 A. Penetration depth 974 B. Specific heat 975 C. Thermal conductivity 975 D. Angle-resolved photoemission 976 III. Half-Integer Flux-Quantum Effect 977 A. Josephson tunneling 977 B. Flux quantization in a superconducting ring 980 C. Paramagnetic Meissner effect 981 IV. Phase-Sensitive Tests of Pairing Symmetry 982 A. SQUID interferometry 982 B. Single-Josephson-junction modulation 984 C. Tricrystal and tetracrystal magnetometry 985 1. Design and characterization of controlledorientation multicrystals 985 2. Magnetic-flux imaging 986 3. Nature of the observed half-integer flux quantization 988 4. Integer and half-integer Josephson vortices 989 5. Evidence for pure d-wave pairing symmetry 993 a. Tetragonal Tl 2 Ba 2 CuO 6ϩ␦ 994 b. Orthorhombic Bi 2 Sr 2 CaCu 2 O 8ϩ␦ 995 D. Thin-film SQUID magnetometry 997 E. Universality of d-wave superconductivity 997 1. Hole-doped cuprates 998 2. Electron-doped cuprates 998 3. Temperature dependence of the ⌽ 0 /2 effect 1000 V. Related Symmetry-Sensitive Experiments 1000 A. Biepitaxial grain-boundary experiments 1000 B. c-axis pair tunneling 1001 1. Tunneling into conventional superconductors 1001 2. c-axis twist junctions 1004 VI. Implications of d x 2 Ϫy 2 Pairing Symmetry 1004 A. Pairing interaction 1004 B. Quasiparticles in d-wave superconductors 1006 C. Surfaces and interfaces 1006 1. Zero-bias conductance peaks 1006 2. Time-reversal symmetry breaking 1007 3. Josephson junctions in d-wave superconductors 1007 D. Vortex state 1007 VII. Conclusions 1008 Acknowledgments 1009 References 1009

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“…It might be attributed to the excessive doping of Ga cation and substitutions of Gd-Ba that make the inter magnetic field induced pinning centers spacing less than or equal to twofold and migration of the magnetic flux line easier. Moreover, there are some possible explanations for the negative effect of the excessive doping of ionic Ga on the pinning of magnetic flux: the creation of a weak-link structure inside grains [13]; the increase of the coherence-length anisotropy ratio ( ) which leads to a smaller tilt modulus of the flux lattice and tends to reduce the overall pinning strengths [14]; the decrease of the ability of the Cu-O chains to couple the Cu-O planes [15]; the decrease of the average free energy per unit length of a vortex (␦G/L) which seem to be correlated with the J c values at 77.3 K in the giant flux creep regime [16]. Fig.…”

Section: Resultsmentioning

confidence: 98%