Asymmetry of the velocity-matching steps in YBCO long Josephson junctions

Abstract

We carry out experimental and theoretical investigations into the effect of the vortex chain propagation on the current-voltage characteristics of YBa 2 Cu 3 O 7−δ (YBCO) long Josephson junctions. Samples of YBCO Josephson junctions, fabricated on 24°[001]-tilt bicrystal substrates, have been measured. The improved technology has allowed us to observe and study the asymmetry of the current-voltage characteristics with opposite magnetic fields (Revin et al 2012 J. Appl. Phys. 114 243903), which we believe occurs due to anisotropy of bicrystal substrates (Kupriyanov et al (2013 JETP Lett. 95 289)). Specifically, we examine the flux-flow resonant steps versus the external magnetic field, and study the differential resistance and its relation to oscillation power for opposite directions of vortex propagation.

THz Properties of Long YBaCuO Bicrystal Josephson Junction Studied with a Cold-Electron Bolometer

“…This ratio is confirmed experimentally: the voltage position of the step for larger fields depends linearly on the applied field [45,50]. The voltage range from 0.2 to 1.1 mV corresponds to Josephson frequencies ranging from about 100 to 550 GHz.…”

“…We observe field dependent steps, characteristic to the travelling wave regime in a long Josephson junction. It should be noted that in difference with Nb junctions [38], for YBCO structures, due to larger damping, it is rather difficult to distinguish between various step types, such as displaced linear slopes, Fiske steps and velocity matching (VM) steps [50,51]. The separate peaks, repeated at the same frequency for all magnetic fields, are attributed to overlapping responses between different harmonics of antennas of YBCO oscillator and CEBs array.…”

Nonmonotonous temperature dependence of Shapiro steps in YBCO grain boundary junctions

“…With the decrease in the temperature, its characteristic dimension increases, and for 20 K, in the general case, Equation 1 becomes invalid, that is, the dynamics of the spatial distribution of the phase and the magnetic field inside the junction becomes important [39][40][41]. In the case of long JJs it is necessary to consider the sine-Gordon equation, taking into account the non-uniform distribution of currents flowing through the barrier, which is typical for bicrystal junctions [28,42,43]. However, if the junction length is of the order of the kink size and there is no external magnetic field, the long junction dynamics is close to that of a short one [39] and the used model is qualitatively adequate.…”

Критический Ток В Длинном Джозефсоновском Контакте Во Внешнем Магнитном Поле При Слабом Пиннинге

“…В этой модели расчеты могут быть выполнены весьма точно, что позволяет разобраться в деталях происходящих процессов. Поэтому процессы в длинных джозефсоновских контактах анализируются в значительном числе работ [7][8][9].…”