Recoupling of Decoupled Vortex Liquid by Columnar Defects inBi2Sr2CaCu2

Abstract

We report on the effect of columnar defects on the interlayer phase coherence in Bi 2 Sr 2 CaCu 2 O 81y using Josephson plasma resonance as a probe. In the vortex liquid phase close to T c , the resonance field (H p ) shows a characteristic exponential temperature dependence similar to that of the irreversibility line. A drastic increase in H p occurs at a frequency-dependent temperature in the vortex liquid phase. We interpret this change as a manifestation of field-induced recoupling of decoupled vortex liquid by columnar defects. The double resonance peaks observed in this temperature range indicate the coexistence of coupled and decoupled vortex regions. [S0031-9007(97)04419-0]

Entropy, vortex interactions, and the phase diagram of heavy-ion-irradiatedBi2Sr2CaCuBeek1, Kończykowski2, Drost3 et al. 2000Phys. Rev. BSelf Cite403290View full textAdd to dashboardCite

“…Note that due to the different effective measurement frequencies, f = 7.753 Hz in the ac shielding experiment versus f ∼ 10 −2 Hz for magnetization measurements using the SQUID, the H irr -values plotted in the Figure lie much above the apparent H irrvalues extracted from the closing of the magnetic hysteresis loops or merger of zero-field-cooled and field-cooled data obtained with a SQUID magnetometer. 8,[11][12][13] The same is indicated in Fig. 1(a), which shows the position of H irr determined from transmittivity measurements on the magnetization curve.…”

“…This is in contradiction to numerical work 57 and previous magnetization studies 13 which reported significant features in the phase diagram at µ 0 H a ≈ 1 3 B φ . Figure 7 shows that, whereas for the values of the matching field B φ = 1 and 2 T, most commonly investigated in the literature, [11][12][13]57 the fraction B φ /3 coincides with the crossover from regime (II) to regime (III) in H irr (T ), this is by no means true for other values of B φ . The results also show that the reported scaling of the irreversibility line with B φ reported in Ref.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] The effect of the ion tracks is twofold. First, the destruction of superconductivity within the columnar defect core, the radius of which is comparable to the superconducting coherence length ξ, leads to a large reduction of the mixed state free energy [14][15][16][17][18] arising from the pinning of the two-dimensional pancake vortices in the superconducting layers 19,20 by the columns.…”

“…4,7,[22][23][24][25] The pancake vortex alignment is manifest in the angular dependence of the transport properties of the irradiated superconductor, 4,6 as well as in measurements of the c-axis conductivity (perpendicular to the superconducting layers) 9,10,26,27 and of the field at which the Josephson plasma resonance occurs in the range 24 -45 GHz. 11,12,28,29 Measurements of the Josephson plasma resonance and of the c-axis conductivity, 26,27 which have the advantage of directly probing the Josephson critical current and the cosine of the average phase difference between layers, show the existence, in the heavy-ion irradiated layered superconductor Bi 2 Sr 2 CaCu 2 O 8+δ , of a regime B l (T ) < B < B h (T ) in the vortex liquid state in which interlayer superconducting phase coherence increases as the magnetic field is increased (i.e. a "recoupling").…”

Equilibrium magnetization in heavy-ion-irradiatedBi2Sr2CaCu2Drost1, Beek2, Heijn3 et al. 1998Phys. Rev. BSelf Cite276210View full textAdd to dashboardCite

“…While the equilibrium magnetization is insensitive to the alignment of pancake vortices, we can compare its results to Josephson plasma resonance ͑JPR͒ experiments that do sense the pancake alignment. 17,18 These experiments directly probe the Josephson critical current along the c axis, itself determined by the relative phase shifts of the order parameter between layers and therefore by the correlations in pancake vortex distribution between the CuO 2 layers. In turn, the JPR cannot sense how many vortices are trapped on a columnar defect; its measurement is thus complimentary to that of the reversible magnetization.…”