High-quality superconducting Josephson junctions on LiNbO3 electro-optical crystals

Abstract

The attainment of high-quality Josephson junctions on electro-optical substrates constitutes a key step toward the fabrication of functional superconducting opto-electronics. We report on the fabrication of high-quality all-refractory niobium superconducting tunnel junctions deposited on X-cut LiNbO3 single crystals. A high quality factor Vm=0.7ΔIgR2mV (where ΔIg is the current jump at the sum gap voltage and R2mV the static resistance at V=2mV) up to 61 mV has been measured at T=4.2K. The very low contribution of subgap leakage currents is demonstrated by the BCS-like quasiparticle current measured at V=0.1mV down to T=1.9K.