Self-heating hotspots in superconducting thin-film microbridges

Abstract

Heating effects in both long and short superconducting thin-film microbridges are described and analyzed. Except near Tc at low voltages where superconducting quantum processes occur, all of our experimental dc I-V characteristics can be satisfactorily understood on the basis of a simple model of a localized normal hotspot maintained by Joule heating. We consider approximations appropriate to the cases of long bridges, short bridges, and bridges coupled to microwave radiation. The analysis leads to analytic expressions for the I-V characteristics which agree well with the experimental data. We show that the formation of such a hotspot is the dominant cause of the hysteresis observed in the I-V characteristics at low temperatures. We also show that the growth of such a hotspot imposes a high-voltage limit on the ac Josephson effect in these devices, and we compare the importance of such heating effects at high voltages in various types of superconducting weak links.

Spin battery operated by ferromagnetic resonance

“…The temperature can be kept low by, e.g., immersing the sample in superfluid helium. The heat transfer is then approximately 8 W/cm 2 K for small temperature gradients and increases for larger temperature gradients, 23 which appears sufficient for the present purpose.…”

Origin of Hysteresis in a Proximity Josephson Junction

“…This interpretation should definitely hold also in shorter metal-based S-N-S junctions where the dissipated power density at the switching is larger. In the case of Josephson junctions based on nanowires [5,9], twodimensional electron gases [8], carbon nanotubes [10], or graphene [11], the power density at the switching is estimated to be about or above 1 nW= m 3 , while the samples investigated here feature generally a smaller density in the range 2 10 ÿ3 to 1 nW= m 3 . This suggests that the observed hysteresis in these other kinds of lateral Josephson junctions is also due to electron heating.…”

“…Two main explanations have been proposed. First, the Joule power deposited in the weak link can induce a self-heating process so that the local temperature in the normal part increases [2,3,12]. Second, it has been proposed that the response time of the junction R n C should be replaced by a time @= related to the superconducting gap [4] or by the electron diffusion time L 2 =D through the junction [6].…”

Astability and Negative Differential Resistance of the Wigner Solid

“…Relaxation oscillations are commonly observed in devices with NDR such as the tunnel diode, diac, and triac [16], in superconducting devices (SD) like the Josephson junction [17] and superconducting microbridges [18], and in CDW [19]. For all of the devices above oscillations develop when biasing in the NDR region, the amplitude of the oscillations is independent of the bias, and the oscillation frequency increases with increasing bias.…”