Dynamics of order parameter and microwave emission for a YBa 2Cu 3O 7− δ bicrystal junction

Abstract

It is shown that the experimental result and the numerical result by using time dependent Ginzburg–Landau (TDGL) equations for the current–voltage characteristics of a YBa 2Cu 3O 7− δ bicrystal junction with a finite excess current agree well. The YBa 2Cu 3O 7− δ bicrystal Josephson junction was fabricated on a MgO(1 0 0) 24° bicrystal substrate and it was integrated with a bow-tie antenna structure for broadband high-frequency coupling. The critical current of the bicrystal junction was 505 μA and there was a finite excess current I ex on the current–voltage characteristics. The microwave emission power per bandwidth of Δf=0.9 GHz at 141 GHz from the same junction was also measured and the total emission power was of the order of 10 −9 W. A schematic model of the order parameter in a weak link, which is dominated by the normalized one-dimensional TDGL equations, is presented. Comparing the experimental result with the numerical result for current–voltage characteristics, the values of ξλ 2=1.88×10 −19 m 3 and σλ 2=7.32×10 −7 Ω −1 m are obtained. By using these values, the microwave emission power of the order of 10 −9 W is estimated. This value is consistent with the experimental result.