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Abstract. This topical review summarizes various features of magnetic penetration depth in unconventional superconductors. Precise measurements of the penetration depth as a function of temperature, magnetic field and crystal orientation can provide detailed information about the pairing state. Examples are given of unconventional pairing in hole-and electron-doped cuprates, organic and heavy fermion superconductors. The ability to apply an external magnetic field adds a new dimension to penetration depth measurements. We discuss how field dependent measurements can be used to study surface Andreev bound states, nonlinear Meissner effects, magnetic impurities, magnetic ordering, proximity effects and vortex motion. We also discuss how penetration depth measurements as a function of orientation can be used to explore superconductors with more than one gap and with anisotropic gaps. Details relevant to the analysis of penetration depth data in anisotropic samples are also discussed.Keywords: penetration depth, unconventional superconductivity, pairing symmetry IntroductionThe early suggestion that high temperature superconductors might exhibit unconventional, d-wave pairing, [24,11,154,8] has lead to a wide variety of new experimental probes with sensitivity sufficient to test this hypothesis. The pioneering work of Hardy and coworkers demonstrated that high resolution measurements of the London penetration depth could detect the presence of nodal quasiparticles characteristic of a d-wave pairing state [87]. Since that time, a large number of new superconductors have been discovered, many of which exhibit nontrivial departures from BCS behavior. As we show in this review, penetration depth measurements can be used to examine not only nodal quasiparticles but two-gap superconductivity, anisotropy of the energy gap, Andreev surface states, nonlinear Meissner effect, interplane transport, proximity coupled diamagnetism, vortex matter and the coexistence of magnetism and superconductivity, to name several problems of current interest.

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“…[160,162]. Some highly unusual nonmonotonic behavior has been reported for electron-doped cuprates [28,147] and BSCCO-2201 [116].…”

Section: Penetration Depth In High-t C Cupratesmentioning

confidence: 99%

“…[160,142] 5. Absolute value of the penetration depth Resonator perturbation methods, whether low or high frequency, provide extremely precise measurements of changes, Δλ, in the penetration depth as a function of an external parameter; typically temperature or magnetic field.…”

Section: Penetration Depth In Anisotropic Samplesmentioning

confidence: 99%

Magnetic penetration depth in unconventional superconductors

Prozorov

Giannetta

2006

Supercond. Sci. Technol.

404

438

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“…This is in disagreement with d-wave and in agreement with our model. The low temperature dependence of the in-plane penetration depth in Hg-1223 [42]seems to be linear, which would indicate the existence of nodes in the gap. The available tunneling [43] data are also suggestive of nodes.…”

Section: Hbccomentioning

confidence: 98%

Multiband model of high-Tcsuperconductors

Combescot¹

1998

Phys. Rev. B

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We propose an extension to other high Tc compounds of a model introduced earlier for YBCO. In the "self-doped" compounds we assume that the doping part ( namely the BiO, HgO, TlO planes in BSCCO, HBCCO, TBCCO respectively ) is metallic, which leads to a multiband model. This assumption is supported by band structure calculations. Taking a repulsive pairing interaction between these doping bands and the CuO2 bands leads to opposite signs for the order parameter on these bands and to nodes whenever the Fermi surfaces of these bands cross. We show that in BSCCO the low temperature dependence of the penetration depth is reasonably accounted for. In this case the nodes are not located near the 45 o direction, which makes the experimental determination of the node locations an important test for our model. The situation in HBCCO and TBCCO is rather analogous to BSCCO. We consider the indications given by NMR and find that they rather favor a metallic character for the doping bands. Finally we discuss the cases of NCCO and LSCO which are not "self-doped" and where our model does not give nodes.

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“…Angle resolved photoemission (ARPES) experiments [2,3] and measurements of the temperature dependence of the penetration depth [4][5][6] both strongly support this scenario, but perhaps the most convincing evidence comes from the elegant measurements of Wollman et al [7] and of Tsuei et al [8] since they do not depend on the microscopic physics of the energy gap, but instead depend only on the order parameter phase.…”

Section: Introductionmentioning

confidence: 99%

BCS to Bose crossover in anisotropic superconductors

Wallington

Annett

2000

Phys. Rev. B

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In this work we use functional integral techniques to examine the nearest neighbour attractive Hubbard model on a quasi-2D lattice. It is a simple phenomenological model for the high-Tc cuprates that allows both extended (non-local) s-and d-wave singlet superconductivity as well as mixed symmetry states. The Hartree-Gor'kov mean field theory of the model has a finite temperature phase diagram which shows a transition from pure s-wave to pure d-wave superconductivity, via a mixed symmetry s + id state, as a function of doping. Including Gaussian fluctuations we examine the crossover from weak-coupling BCS superconductivity to the strong-coupling Bose-Einstein condensation of composite s-or d-wave bosons and comment on the origin and symmetry of the pseudogap.

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Anisotropic magnetic penetration depth of grain-alignedHgBa2Ca2

Cited by 70 publications

References 25 publications

Magnetic penetration depth in unconventional superconductors

Magnetic penetration depth in unconventional superconductors

Multiband model of high-Tcsuperconductors

BCS to Bose crossover in anisotropic superconductors

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