Suppression of the vortex glass transition due to correlated defects with a persistent direction perpendicular to an applied magnetic field

Abstract

It is found in terms of the lowest Landau level approach for the Ginzburg-Landau model that, in bulk type II superconductors with correlated defects, such as columnar defects, with a persistent direction perpendicular to an applied field H, a continuous vortex-glass transition should be depressed to a low enough temperature in the limit of weak point disorder. Based on this finding, remarkable reductions of the glass transition temperatures, seen in twin-free YBCO with columnar defects in H ⊥ c and twinned YBCO in H c, are discussed. It is pointed out that, in both of these two situations, the critical scaling of vanishing resistivities is anisotropic in spite of an isotropic scaling of correlation lengths and hence, makes it possible to determine two critical exponents by changing the relative angle between the current and the correlated defects.PACS numbers: 74.20. De, 74.25.Fy, 74.40.+k, 74.25.Qt, 74.72.Bk It is well understood that, in three-dimensional (3D) type II superconductors with correlated line defects, a continuous vortex-glass transition (the so-called Boseglass transition) [1] should occur in nonzero magnetic fields parallel to the line defects. Since this glass ordering is conceptually and formally equivalent to the corresponding quantum transition in 2D case, it should be described according to Ref.[2] as a long-ranged phase coherence measured by the glass correlation functionwhich was introduced to describe the vortex-glass transition in 3D due to point defects [3]. Here, ψ is the pairfield, denotes the thermal average, and [ ] implies the average over a quenched randomness. Examining eq.(1) under the Ginzburg-Landau (GL) hamiltonian [4]with random potentials u and f is a natural starting point for understanding a glass transition, characterized by the disappearance of the Ohmic resistance, in vortex states as far as the transition is continuous [3,4,5,6], where, and φ 0 is the flux quantum.In this note, we argue that, in a field perpendicular to strong line disorder, such a continuous vortex-glass transition does not occur at nonzero temperatures as far as no point disorder is present, and hence that, with increasing point disorder, the (dimensionless) glass transition temperature t G = T G /T c0 in this case is elevated in contrast to the case [7] with no line disorder, where T c0 is the zero field transition in each sample. Our interest in phenomena in this field configuration was motivated by an observation [8] in twin-free YBCO with heavy-ions irradiated along the c-axis. In contrast to the material (intrinsic) anisotropy on the width of the vortex-liquid region between H c and H ⊥ c cases in a unirradiated sample of cuprates, the vortex-liquid region of an irradiated sample in H ⊥ c is much wider, in particular in lower H, compared with the corresponding one in H c and has almost the same extent as that of the unirradiated sample in H c. Although, at the microscopic level, a heavy-ion irradiation in cuprates may correspond to an overdoping and hence, lead to a reduction of the intrinsi...

Effect of In-Plane Line Defects on Field-Tuned Superconductor–Insulator Transition Behavior in Homogeneous Thin Film

“…In the expressions of these diagrams, the vortex-glass correlation function Gvg (k ; ω, ω +Ω) inducing the ξ vg -dependences is included. In the present case with line defects perpendicular to the field, Gvg has been studied elsewhere 10 and, in the so-called ladder approximation, becomes…”

“…In eq. (10) giving the SC fluctuation propagator G(ω) selfconsistently, a fluctuation renormalization of the bare pinning strengths ∆ w (w = p, l) will be incorporated by replacing them by ∆ w /(1 + v p ),…”