Quantum dynamics of a d-wave YBCO Josephson junction

Hisashi Shimakage, Yoshinori Uzawa, Zhen Wang

Shiro Kawabata, Alexander A. Golubov, Ariando Ariando +2 more

Shiro Kawabata, Takeo Kato, Floriana Lombardi +1 more

Shiro Kawabata, Thilo Bauch, Takeo Kato

We investigate classical thermal activation (TA) and macroscopic quantum tunneling (MQT) for a ${\text{YBa}}_{2}{\text{Cu}}_{3}{\text{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ (YBCO) Josephson junction coupled to an LC circuit theoretically. Due to the coupling between the junction and the LC circuit, the macroscopic phase dynamics can be described as the escape process of a fictitious particle with an anisotropic mass moving in a two-dimensional potential. We analytically calculate the escape rate including both the TA and MQT regime by taking into account the peculiar dynamical nature of the system. In addtion to large suppression of the MQT rate at zero temperature, we study details of the temperature dependence of the escape rate across a crossover region. These results are in an excellent agreement with recent experimental data for the MQT and TA rate in a YBCO biepitaxial Josephson junction. Therefore the coupling to the LC circuit is essential in understanding the macroscopic quantum dynamics and the qubit operation based on the YBCO biepitaxial Josephson junctions.

K. Y. Constantinian, G. A. Ovsyannikov, I. V. Borisenko +2 more

We measured spectral noise density in YBCO symmetric bicrystal Josephson junctions on sapphire substrates at bias voltages up to 100 mV and T=4.2 K. Normal state resistance of the Josephson junctions, R/sub N/=20-90 /spl Omega/ and I/sub C/R/sub N/ 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/spl les/V/spl les/60 mV a linear voltage dependence of noise power has been registered, while at V/spl les/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 d-wave superconducting electrodes.

Floriana Lombardi, Thilo Bauch, Jesper Johansson +4 more