Flux-pinning and inhomogeneities or defects in amorphous superconducting Mo5Ge3 films

Yoshizumi, S.; Carter, William L.; Geballe, T. H.

doi:10.1016/0022-3093(84)90610-0

Cited by 21 publications

(9 citation statements)

References 4 publications

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“…Experimental studies [5,6] of the critical current of relatively thick superconducting films with weak pinning are in very good agreement with the predictions of this theory. Direct studies of the zero bias resistance (dV/dl as /-• 0) are not so highly developed.…”

supporting

confidence: 79%

“…The thickest film (^=300 A) has J c~~ 10 3 A/cm 2 . From previous measurements [6], we know that the bulk zero temperature coherence length is £(0)=55 A, and the bulk penetration depth is X^^llOO A, yielding a perpendicular penetration depth X_L(0) = ^2(0)A/ 5 that ranges from 100 jxm when dy =60 A to 20 /im when d s =300 A. Finally, we note that, for all of our films, the characteristic vortex bending lengths due to either thermal fluctuations [7] or pinning potentials [3] are orders of magnitude greater than the thicknesses of our films, so the 2D limit applies.…”

mentioning

confidence: 99%

“…With multitarget sputtering, we have prepared films with nominal thickness d s ranging from 60 to 300 A, as described previously [6]. The samples and their parameters are shown in Table I.…”

mentioning

confidence: 99%

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Collective vortex motion ina-MoGe superconducting thin films

1993

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We report linear and nonlinear electrical transport in perpendicular magnetic fields of very thin amorphous Mo79Ge2i superconducting films. At low fields, we demonstrate the existence of a barrier to vortex motion away from the sample edges. In regimes where the vortex motion is not substantially affected by the sample edges, we observe manifestly collective activated behavior. We relate the field dependence of the observed activation energies to possible mobile configurations of vortices.

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confidence: 79%

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confidence: 99%

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Collective vortex motion ina-MoGe superconducting thin films

1993

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“…Estimates of R c obtained from the critical current measurements on similar samples [19] based on LO theory [12] are about an order of magnitude smaller than the typical R^. While this discrepancy may reflect the inaccuracy of the criteria used in estimating the value of R c , it may also be a consequence of the method of probing the correlated volumes in each experiment.…”

Section: ] Melting Transition In the Two-dimensional Vortex Lattice mentioning

confidence: 85%

Observation of Kosterlitz-Thouless-type melting of the disordered vortex lattice in thin films ofa-MoGe

et al. 1993

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Measurements of the ac penetration depth of a-MoGe films in the presence of a perpendicular magnetic field reveal an anomaly in the ac response of the vortex lattice at a characteristic temperature below the H c i(T) line. The field and frequency dependence of this anomaly is found to be consistent with a Kosterlitz-Thouless-type melting of the two-dimensional vortex lattice. Moreover, we observe a crossover in the frequency dependence which suggests that the vortex lattice remains disordered on long length scales below the melting temperature.PACS numbers: 74.60.Ec, 74.60.GeThe question of the existence of a finite-temperature phase transition within the vortex state of type-II superconductors has received considerable attention since the discovery of the high-T^ superconductors. One possible phase transition in these superconductors, as well as conventional superconductors with reduced dimensions, is the dislocation-mediated Kosterlitz-Thouless (KT) [1] melting transition in the two-dimensional vortex lattice (VL). In conventional superconductors, the possibility of this phase transition was first suggested by Huberman and Doniach [2] and by Fisher [3]. At the transition, the solid vortex lattice phase which contains thermally created bound pairs of dislocations, melts as these pairs dissociate at large distances to create free dislocations. However, as Larkin [4] showed long ago, in the solid phase, any amount of disorder will disturb the lattice on long length scales, hence limiting positional correlations to a length scale R c > The consideration of disorder raises two important questions: (1) Can the disordered VL "melt locally" as each correlated volume (vortex bundle) melts internally via a KT-type transition with increasing temperature? (2) Do these correlated volumes freeze into a glasslike state at a lower temperature [5]?To date, there are two reports of experiments that have been interpreted as evidence for KT-type melting of the VL. The vibrating-reed experiments of Gammel, Hebard, and Bishop [6] on amorphous composite In/InO x films showed a large dissipation peak at around the predicted melting temperature. However, recently Brandt [7] has argued that these experimental results are likely related to a size-dependent electromagnetic crossover rather than the melting of the VL. The other case is the resistivity and I-V measurements of Berghuis, van der Slot, and Kes [8] on films of a-NbGe. These experiments were interpreted as a crossover of a pinned VL with a finite critical current at low fields to a melted vortex fluid with flux flow resistance at high fields. The crossover was found to occur close to the expected phase boundary.In this Letter, we present evidence for the existence of a melting transition on short length scales in the disordered VL by studying the behavior of the ac penetration depth of amorphous Mo77Ge23 thin films in the presence of a perpendicular magnetic field. Specifically, we interpret observed abrupt changes in the ac penetration depth as evidence for melting of the two-d...

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“…Mo x Ge 1Àx films over a wide range of composition encompassing the insulator/metal (64) and superconducting transitions (65,66). It made possible investigations into the superconducting properties of fine-scaled transition-metal multilayered films (67,68).…”

Section: Stanfordmentioning

confidence: 99%

Why I Haven't Retired

Geballe

2013

Annu. Rev. Condens. Matter Phys.

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What is written below is, as requested by the editor of AR Condensed Matter Physics, a set of recollections and insights gained from my personal trajectory that starts from my earliest years and continues on until now. I have been a participant in the growth of solid state physics from its early quantum insights to the highly popular foci of today's vibrant condensed matter science community, while working at three institutions that helped spearhead this growth-UC Berkeley, Bell Labs, and Stanford University. It is rare to be actively involved in any creative enterprise for more than six decades. I credit my good fortune to stimulating science; great students and colleagues; a happy home; warm friendships; and, evidently, to my having inherited good genes.

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Flux-pinning and inhomogeneities or defects in amorphous superconducting Mo5Ge3 films

Cited by 21 publications

References 4 publications

Collective vortex motion ina-MoGe superconducting thin films

Collective vortex motion ina-MoGe superconducting thin films

Observation of Kosterlitz-Thouless-type melting of the disordered vortex lattice in thin films ofa-MoGe

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