Quantitative theory of transport in vortex matter of type-II superconductors in the presence of random pinning

Abstract

We quantitatively describe the competition between interactions, thermal fluctuations, and random quenched disorder using the dynamical Martin-Siggia-Rose approach ͓Phys. Rev. A 8, 423 ͑1973͔͒ to the Ginzburg-Landau model of the vortex matter. The approach first used by Dorsey et al. ͓Phys. Rev. B 45, 523 ͑1992͔͒ to describe the linear response far from H c1 is generalized to include both pinning and finite voltage. It allows one to calculate the non-Ohmic I-V curve, thereby extending the theory beyond the linear response. The static flux line lattice in type-II superconductors undergoes a transition into three disordered phases: the vortex liquid ͑not pinned͒, the homogeneous vortex glass ͑pinned, if one disregards an exponentially small creep at finite tem-peratures͒, and the crystalline Bragg glass ͑pinned͒ due to both thermal fluctuations and disorder. The location of the glass transition line in the homogeneous phase is determined and compared to experiments. The line is clearly different from both the melting line and the second peak line describing the translational and rotational symmetry breaking at high and low temperatures, respectively. Time correlation and response functions of the order parameter as functions of the time difference are calculated in both the liquid and the amorphous homogeneous phases. They determine the relaxation properties of the vortex matter due to the combined effect of pinning and thermal fluctuation. We calculate the critical current as a function of magnetic field and temperature in the homogeneous phase. The surface in the J-B-T space defined by this function separates between a dissipative moving vortex matter regime and vortex glass. A quantitative theory of the peak effect, qualitatively different from the conventional one due to Pippard ͓C.

Creep and depinning of vortices in a nontwinned YBa2Cu3O6.87 single crystal

“…3 [11], which predicts monotonous decrease of this current with increased field. Also, gradual increase of the current J d contradicts with the quantitative theory of Rosenstain and Zuravlev [14], which predicts a jump-like increase of this currents at the OD transition. Therefore we can assume that increase in the pinning force is associated with gradual transition from the ordered to disordered VS phase as it was proposed by Ertas and Nelson [13].…”

“…[12]. Two alternative explanations [13,14] predict transformation of an ordered vortex solid (VS) phase, which forms in low fields and is characterized by a decrease of the force F p with increased field, to a disordered VS phase, which forms in high fields and is characterized by increase of the force F p with the field. These models are supported by correlation between the field H OD corresponded to an ordering in the VS structure [15] and onset of the F p increase [7] in BiCaSrCuO crystals.…”

Order-disorder transition and flow noise for vortices in amorphous films

“…When a moderately strong current is applied, the DP survives annealing over the relevant experimental time scales. The coexistence of OP and DP in fields below B p is not unreasonable, considering a supercooled metastable DP in the OP [1,5,6,13] and/or possible slight inhomogeneities of a-Mo x Ge 1−x films. The metastability mentioned here may also account for the absence of the sharp peak in I c (B) in our a-Mo x Ge 1−x films.…”

Vortex states in the peak effect regime of films probed by noise

“…In the mixed state of conventional ðlow-T c Þ superconductors the vortex states near the peak effect (PE) regime, where the critical (depinning) current I c shows a peak with magnetic field B or temperature T, have attracted considerable interest [1][2][3][4][5][6][7]. The PE originates from softening of the vortex lattice just prior to melting, or disorder-induced destruction of long-range order.…”