Experimental Evaluation of Self-Heating Effect in Intrinsic Josephson Junctions Using Pulse Current Measurements

Abstract

Intrinsic Josephson junctions (IJJs) in layered high-critical-temperature superconductors such as single-crystal Bi 2 Sr 2 CaCu 2 O 8+ δ (Bi-2212), which comprises several atomically stacked Josephson junctions, have been intensively studied, and it is known that the current-voltage (I-V ) characteristics of IJJs are affected by self-heating. Therefore, evaluating the self-heating effect in the IJJs is important. Pulse current measurement techniques are commonly employed to reduce the self-heating effect. However, in mesa-type IJJ samples, self-heating occurs not only owing to the applied voltage in voltage-state IJJs, but also owing to the contact resistance between the electrode and the top of the mesa. It has been found in previous studies, for small samples with good electrode contacts, that an electrode on the top of the mesa can help to cool the mesa. However, the effect of heating owing to the contact resistance has not been well studied in large samples. In this paper, the I-V and self-heating characteristics of mesa-type IJJs were experimentally investigated for devices wherein self-heating was suppressed using pulse current measurements. Furthermore, to evaluate the contact resistance effect on the I-V characteristics, we proposed a new pulse waveform, because when using the conventional pulse measurement, the voltage values of the quasiparticle branch were much larger than those obtained via the dc measurement. We measured the I-V characteristics using this waveform to determine the effect of heat generation that occurs due to the contact resistance between the electrode and the top of the mesa. We found that in this case, the voltage was considerably suppressed.