Current–voltage characteristics of dc voltage biased high temperature superconducting microbridges

Abstract

We have investigated the dc current–voltage characteristic of high temperature superconducting microbridges. When a dc voltage is applied to a microbridge, it switches to a lossy state due to the formation of a hotspot in the bridge. We have measured the length and temperature of the hotspot as a function of the applied voltage, and have developed a thermal model to explain its steady state behavior. The hotspot has a flat-topped temperature profile, with the maximum temperature independent of the applied voltage. The length of the hotspot, and hence the bridge resistance, increases linearly with the applied bias, so the current is independent of the applied voltage once switching has occurred.

Thermal behaviour of high-temperature superconducting fault current limiters: Application to microlimiters

“…with n ¼ 3/2 for I * [11,12] and 1/2 for I min [18][19][20]. Therefore, if the reduced temperature increases both the discontinuity at V * and the ratio I * /I min will decrease, in agreement with the results of Fig.…”

“…Note first that, once the source voltage overcomes V * , the current in the circuit varies quite slowly even up to voltage faults as important as four times V * , the current taking a minimum value, I min , at some (temperature-dependent) voltage. Moreover, the sharp drop at V * of the current is also temperature dependent, being almost absent in the curve at 85.0 K. Both aspects are related and may be explained in terms of the approaches based on the propagation of self-heating hot spots [18][19][20]: Above V * part of the microbridge becomes normal and then, as the total voltage of the circuit is fixed, the resistance increase originates a current decrease up to the minimum current, I min , capable of sustaining the normal zone. If the fault voltage increases, the hotspot length will grow accordingly, keeping the current roughly constant.…”

Ultrafast photoresponse in microbridges and pulse propagation in transmission lines made from high-T/sub c/ superconducting Y-Ba-Cu-O thin films

“…3. The curves are typical for a superconducting YBCO microbridge [25]. One can clearly distinguish the two different voltage states-the superconducting/flux-flow state with zero/low voltage across the bridge and the switched state where the current is almost constant while the voltage across the bridge increases as the bias is increased.…”

“…When the generated heat is more than the surrounding cryogen can dissipate, a hot spot forms in the microbridge and it switches to a state with lower current and higher voltage. In the hot spot, the temperature is roughly constant, equal to , where is the bath temperature [25]. If the microbridge is long, the hot spot initially covers only part of the bridge, giving rise to a constant-current (plateau) region as the hot-spot size increases.…”

Analytic thermal modeling for dc-to-midrange modulation frequency responses of thin-film high-T_c superconductive edge-transition bolometers

“…However, this would not be the case for devices exposed to high radiation intensities that are normally voltage biased for further stability. 23,24 The effect of the bias configuration on the response and the feedback effect of the joule heating for each case of the voltage-biased and current-biased configurations are discussed and presented elsewhere. 13 There is also a consecutive temperature variation that is due to ac joule heating in the film caused by the resistance variation in the superconducting film that is due to the input radiation power.…”