Josephson (001) tilt grain boundary junctions of high-temperature superconductors

Abstract

We calculate the Josephson critical current Ic across in-plane (001) tilt grain boundary junctions of high temperature superconductors. We solve for the electronic states corresponding to the electrondoped cuprates, two slightly different hole-doped cuprates, and an extremely underdoped holedoped cuprate in each half-space, and weakly connect the two half-spaces by either specular or random Josephson tunneling. We treat symmetric, straight, and fully asymmetric junctions with s-, extended-s, or d x 2 −y 2 -wave order parameters. For symmetric junctions with random grain boundary tunneling, our results are generally in agreement with the Sigrist-Rice form for ideal junctions that has been used to interpret "phase-sensitive" experiments consisting of such in-plane grain boundary junctions. For specular grain boundary tunneling across symmetric junctions, our results depend upon the Fermi surface topology, but are usually rather consistent with the random facet model of Tsuei et al. [Phys. Rev. Lett. 73, 593 (1994)]. Our results for asymmetric junctions of electrondoped cuprates are in agreement with the Sigrist-Rice form. However, our results for asymmetric junctions of hole-doped cuprates show that the details of the Fermi surface topology and of the tunneling processes are both very important, so that the "phase-sensitive" experiments based upon in-plane Josephson junctions are less definitive than has generally been thought.

Transport properties of variable-angle YBa2Cu3O7 − δstep-edge junctions in thea–bplane

“…Further theoretical modelling of the I c (T ) behaviour in stepedge and [100]-tilt junctions might explain the discrepancies between theory and experiment. We note that our I c (T ) measurements for the θ = 19 • and 28 • junctions in figure 7 (those corresponding most closely with the (130) and (120) junctions, respectively in [45]) did not show the anomaly predicted for (120) junctions [45], although this predicted anomaly has more recently been disputed [65].…”

BCS-BEC model of high-Tc superconductivity in layered cuprates with unconventional pairing

“…Ref. [15] summarizes many of the problems with the so-called "phase-sensitive" tests [16] in YBCO. Additionally, predictions made in Ref.…”

Anisotropic distributions of electrical currents in high-T c grain-boundary junctions

“…Among a variety of possible crystallographic orienta tions of grains forming a boundary, the [001] tilt GB (see Fig. 1a) had been studied the most intensively with an emphases on the effect of order parameter symmetry and the mechanisms of charge transfer across the GB interface [1,2,[7][8][9][10][11][12][13][14][15].…”

“…Among a variety of possible crystallographic orienta tions of grains forming a boundary, the [001] tilt GB (see Fig. 1a) had been studied the most intensively with an emphases on the effect of order parameter symmetry and the mechanisms of charge transfer across the GB interface [1,2,[7][8][9][10][11][12][13][14][15].Recently, [100] tilt high T c GB junctions with mutually tilted c axis's (see Fig. 1b) have been fabri cated [16][17][18][19][20][21][22][23][24][25] with an order of magnitude lower GB meandering and up to a threefold increase of the I c R n values [16][17][18][19].…”