Long-range Quasiperiodic Order Research Articles

Phase coherence and dynamics in weakly-coupled periodic and quasiperiodic superconductor arrays

We have fabricated and studied the transport properties of arrays of proximity-coupled superconductor islands arranged in a quasiperiodic Penrose tile geometry. In the magnetic field response, we identify coarse structure arising from the irrational area ratio of the two fundamental tile shapes, and fine structure due to the long-range quasiperiodic order of the array. By varying the voltage bias of the sample, which governs the rate of vortex diffusion, we can adjust the range of phase coherence in the array and identify the origin of specific features in the magnetoresistance. These ideas have been corroborated by measurements on ladder arrays with varying widths and on periodic arrays with two irrationally-related cell areas. Measurements of the resistive transition and nonlinear current-voltage characteristics are consistent with a Kosterlitz-Thouless vortex-unbinding phase transition at zero field, but show more complicated behavior at finite fields.

Resistive transition and magnetic field response of a Penrose-tile array of weakly coupled superconductor islands.

We have studied the effects of geometry- and magnetic-field-induced frustration on the transport properties of a Penrose-tile array of proximity-coupled superconductor islands. The arrays exhibit a broad transition to a zero-resistance state at a field-dependent critical temperature. Above this temperature, the resistance of the array modulates quasiperiodically with applied field. Measurements at different excitation levels distinguish structure arising from the irrational tile area ratio in the Penrose pattern from fine structure generated by the long-range quasiperiodic order.