Stephen W. Pierson

DYNAMIC SCALING FOR TWO-DIMENSIONAL SUPERCONDUCTORS, JOSEPHSON-JUNCTION ARRAYS, AND SUPERFLUIDS

The value of the dynamic critical exponent {ital z} is studied for two-dimensional superconducting, superfluid, and Josephson junction array systems in zero magnetic field via the Fisher-Fisher-Huse dynamic scaling. We find z{approx_equal}5.6{plus_minus}0.3, a relatively large value indicative of nondiffusive dynamics. Universality of the scaling function is tested and confirmed for the thinnest samples. We discuss the validity of the dynamic scaling analysis as well as the previous studies of the Kosterlitz-Thouless-Berezinskii transition in these systems, the results of which seem to be consistent with simple diffusion (z=2). Further studies are discussed and encouraged. {copyright} {ital 1999} {ital The American Physical Society}

Zero-field current-voltage characteristics in high-temperature superconductors

Abstract Zero-field current-voltage ( I - V ) data from a variety of samples of various high-temperature superconductors are re-analyzed to test the recently proposed current-temperature ( I - T ) phase diagram [S.W. Pierson, Phys. Rev. Lett. 74 (1995) 2359]. It is found that the I - V curves are well-described by this phase diagram. Furthermore, because the slopes of the various phase lines can be related to the effective interlayer coupling, it is shown that the I - T phase diagram provides a convenient framework in which to characterize samples. We discuss how the structure of the I - T phase diagram can be further tested and how more can be learned about these materials by probing parts of the I - T phase space which most experiments have neglected. Finally, further details of the I - T phase space are discussed.

THREE-DIMENSIONAL LOWEST-LANDAU-LEVEL THEORY APPLIED TO YBA2CU3O7-DELTA MAGNETIZATION AND SPECIFIC HEAT DATA : IMPLICATIONS FOR THE CRITICAL BEHAVIOR IN THE H-T PLANE

We study the applicability of magnetization and specific heat equations derived from a lowest-Landau-level (LLL) calculation, to the high-temperature superconducting (HTSC) materials of the YBa

Current-temperature phase diagram of layered superconductors

_2

A review of the real space renormalization group analysis of the two-dimensional Coulomb gas, the Kosterlitz-Thouless-Berezinski transition, and extensions to a layered vortex gas

Cu

Renormalization group study of the intrinsic finite-size effect in two-dimensional superconductors

_3

Dynamic scaling of I–V data for the neutral 2D Coulomb gas

O

Flux-lattice melting and lowest-Landau-level fluctuations

_{7-\delta}

Flux lattice melting and the onset of Hc2 fluctuations

(YBCO) family. We find that significant information about these materials can be obtained from this analysis, even though the three-dimensional LLL functions are not quite as successful in describing them as the corresponding two-dimensional functions are in describing data for the more anisotropic HTSC Bi- and Tl-based materials. The results discussed include scaling fits, an alternative explanation for data claimed as evidence for a second order flux lattice melting transition, and reasons why 3DXY scaling may have less significance than previously believed. We also demonstrate how 3DXY scaling does not describe the specific heat data of YBCO samples in the critical region. Throughout the paper, the importance of checking the actual scaling functions, not merely scaling behavior, is stressed.

Zero-field current-voltage characteristics in high-Tc superconductors

The behavior of clean layered superconductors in the presence of a finite electric current and in zero-magnetic field behavior is addressed. The structure of the current temperature phase diagram and the properties of each of the four regions will be explained. We will discuss the expected current-voltage and resistance characteristics of each region as well as the effects of finite-size and weak disorder on the phase diagram. In addition, the reason for which a weakly non-Ohmic region exists above the transition temperature will be explained. {copyright} {ital 1997} {ital The American Physical Society}