Shot noise in YBCO bicrystal Josephson junctions

Abstract

We measured spectral noise density in YBCO symmetric bicrystal Josephson junctions on sapphire substrates at bias voltages up to 100 mV and = 4 2 K. Normal state resistance of the Josephson junctions, = 20-90 and up to 2.2 mV have been observed in the experimental samples. Noise measurements were carried out within frequency bands of 1-2 GHz and 0.3-300 kHz. At bias voltages 10 60 mV a linear voltage dependence of noise power has been registered, while at 5 mV a noticeable noise rise has been observed. The latter may explain the experimentally measured linewidth broadening of Josephson oscillations at mm and submm wave frequencies in high-Tc superconducting junctions. Experimental results are discussed in terms of bound states existing at surfaces of-wave superconducting electrodes.

Josephson effect in cuprate superconducting structures

“…We see an increase in the effective charge, characteristic for superconducting structures with multiple Andreev reflection. 5,7,44 The maximum value of Q max exceeded 10 e (where e is the charge on the electron).…”

“…Low-energy Andreev states are manifested in bicrystal junctions of CS -both in electrophysical characteristics 3,4 and in the appearance of excess shot noise at low voltages. [5][6][7][8] Note that noise measurements give additional information about the conduction mechanism in the JJ.…”