Adjustment of self-heating in long superconducting thin film NbN microbridges

Abstract

The self-heating in long superconducting microbridges made from thin NbN films deposited on top of high silicon mesa structures was studied by analyzing the hysteresis current density jH. We observed a more than twofold decrease of jH with increase in the ratio of the height of the Si mesa, h, to the width of the microbridge, W, from 0 to 24. We describe our experimental results using one-dimensional thermal balance equations taking into account disordered matter in our thin NbN films and limitations imposed on the phonon mean free path by the width of the Si mesa. In the framework of this model we obtain a good agreement between theory and experiment over a wide temperature range from 4.2 K up to the critical temperature TC for all h/W ratios.

Thermo-magnetic stability of superconducting films controlled by nano-morphology

“…It agrees well with the previously reported results. 28 As confirmed Stockhausen et al, 27 the different measurement conditions for TMI (in vacuum) and the hysteresis current (in low pressure exchange gas) do not influence the thermal coupling of the SC strips to the environment. Nano-defects, in the granular sample A, serve as pinning sites and provide a very homogeneous pinning landscape for the vortices, almost tripling the critical current density with respect to the smooth sample B.…”

“…(1), it factors out and does not change the character of the singular behavior of ' Ã . The heat transfer into the substrate was evaluated from the hysteresis current of the (I-V) curves, 26,27 which were measured in microbridges made of satellite films, i.e., the ones deposited in the same batches with the samples: h 0;A ð4KÞ % 2:49 Â 10 5 Wm À2 K À1 and h 0;B ð4KÞ % 4:64 Â 10 5 Wm À2 K À1 . It agrees well with the previously reported results.…”

Transport properties of ultrathin YBa2Cu3O7−δ nanowires: A route to single-photon detection

“…1). The hysteresis is a distinctive feature of the formation and development of a self-stabilizing hotspot in the superconducting wire [25,26], and it is a consequence of the low value of thermal conductivity in this material (κ ≈ 10 −2 − 10 −1 Wm −1 K −1 in the normal state). Finally, high sheet resistance values make the nanowire resistance much higher that the external load resistance R L (typically 50 Ω) in parallel with the device, so favoring the redistribution of all the bias current into the readout line, where the signal appears.…”

Proximity effect model of ultranarrow NbN strips

“…5). The density of the retrapping current characterizes thermal coupling between the strip and the substrate and depends on the resistivity of superconductor in the normal state and on the difference between TC and the bath temperature Tb at which the current-voltage characteristic is measured [35]:…”