Relaxation oscillator using hysteretic current-voltage characteristics of YBaCuO thin strips

It is shown that thin strips of YBaCuO with high critical current densities j_c(4.2 K)>10⁶ A/cm² exhibit hysteresis in their current-voltage (I-V) characteristics, typically in the normalized temperature region T/T_c⩽0.8. The hysteretic I-V characteristic is used as an active element to construct a relaxation oscillator, i.e. the YBaCuO strip is shunted with an external inductance and a resistance. It is shown that parameter dependencies of the oscillation frequency agree with the previous theoretical results obtained in the conventional Josephson junctions. The relative linewidth of the oscillation is 10^-3 at a typical frequency f=7 MHz, which is comparable to that of the conventional Nb nanobridge. Optical response of the relaxation frequency is also measured in order to study the possibility of utilizing the relaxation oscillator as an optical sensor