Observation of weak coupling effects in Ba sub(0.6)K sub(0.4)Fe sub(2)As sub(2) junctions patterned across a naturally formed grain boundary

We have fabricated intergrain nanobridge junctions from a Ba sub(0.6)K sub(0.4)Fe sub(2)As sub(2) film and observed their weak coupling effects. We prepared the junction by patterning a nanobridge across a natural grain boundary by using a focused ion beam etching technique and studied their superco...

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Published inSuperconductor science & technology Vol. 27; no. 5; pp. 1 - 5
Main Authors Hong, Sung-Hak, Lee, Nam Hoon, Kang, Won Nam, Lee, Soon-Gul
Format Journal Article
LanguageEnglish
Published 01.05.2014
Subjects
Constants
Fluctuation
Grain boundaries
Joining
Nanostructure
Superconductor junctions
Superconductors
Theorems
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Summary:We have fabricated intergrain nanobridge junctions from a Ba sub(0.6)K sub(0.4)Fe sub(2)As sub(2) film and observed their weak coupling effects. We prepared the junction by patterning a nanobridge across a natural grain boundary by using a focused ion beam etching technique and studied their superconducting transition properties. The resistive transition showed three steps: the transitions of the bulk, the microbridge, and the junction grain boundary. Current-voltage curves showed typical Josephson junction characteristics, well--matched with the model of a resistively shunted junction incorporated with thermal fluctuations. Fitting data to theory revealed much larger current fluctuations than expected from the Johnson-Nyquist theorem. The junction showed a linear temperature dependence of the critical current and a constant normal-state resistance, indicating that the grain boundary played a role as a tunnel barrier with a very poor conductance.
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ISSN:0953-2048
1361-6668
DOI:10.1088/0953-2048/27/5/055007