Random telegraph voltage noise in a Bi2Sr2CaCu2O8+x intrinsic Josephson junction

Low frequency noise properties have been investigated in mesa-type Bi₂Sr₂CaCu₂O_8+x (BSCCO) intrinsic Josephson junction. The junction area for this mesa was 160 μm×40 μm. The mesa showed highly hysteretic current-voltage characteristic at low temperatures, and had seven discrete-resistive-branches. For the noise measurements only at T~36 K, we observed a rapid increase in the noise voltage spectrum over our entire bandwidth. Large random telegraph voltage noises (RTVN) were only detected for low bias current region of the BSCCO mesa for current biased on the 4th (I_b=6.0 mA) and 5th (I_b=5.0 mA) resistive-branches, and also not observed for all of voltage region at 4.2 K and low bias voltage region, from 1st to 3rd resistive-branches, at 36 K. The measured S_v(f) had the Lorentzian frequency dependence, as expected from the Machlup formula for random telegraph signal. The possible origin of the large RTVN may be thermal fluctuation of the “switchback” voltage V_min