Experimental evidence for hotspot and phase-slip mechanisms of voltage switching in ultrathin YBa2Cu3O7–x

Abstract

We have fabricated ultra-thin YBa2Cu3O7-x nanowires with a high critical current density and studied their voltage switching behavior in the 4.2 -90 K temperature range. A comparison of our experimental data with theoretical models indicates that, depending on the temperature and nanowire cross section, voltage switching originates from two different mechanisms: hotspot-assisted suppression of the edge barrier by the transport current and the appearance of phase-slip lines in the nanowire. Our observation of hotspot-assisted voltage switching is in good quantitative agreement with predictions based on the Aslamazov-Larkin model for an edge barrier in a wide superconducting bridge. I. INTRODUCTIONOver the last decade, superconducting nanowires have attracted attention because of their promising applications in quantum sensing and computing [1][2][3]. Abrupt voltage switching is a characteristic feature of superconducting nanowires and is used to investigate superconductivity in low-dimensional structures, as well as for practical applications. Voltage switching is observed in both low-temperature (low-Tc) and high-temperature (high-Tc) current-biased superconducting bridges [4][5][6][7][8][9][10][11][12][13][14][15][16]. Voltage switching in conventional low-Tc superconducting bridges is well understood [4][5][6][7][16][17][18]. However, there is no consensus for explaining the origin of voltage switching in high-Tc cuprate superconductors. Several mechanisms have been considered to explain discontinuities in the current-voltage (IV) characteristics of high-Tc superconducting bridges, including flux-flow instabilities [8,[13][14][15], a phase-slip process [11], hotspot effects [8,12], and fluctuating charge stripe domains [10]. In wide and thick bridges, all of these mechanisms can coexist within the same current range, which complicates the analysis of experimental data. However, the identification of voltage switching mechanisms is possible in superconducting wires whose dimensions approach the characteristic length scales of the superconducting state. As a result of the *

Energy-level quantization and single-photon control of phase slips in YBa2Cu3O7–x nanowires

“…Figure 1b shows a scanning electron micrograph of a representative nanowire patterned using focused ion beam (FIB) milling across a 10-μm-wide microbridge. All of the nanowires showed current-voltage (IV) curves that were characteristic of phase slippage, as described in previous work 22 . Based on the linear dependence of the critical current and normal-state resistance on nominal nanowire width and thickness, we determined the effective nanowire width and thickness that we use below rather than the nominal ones.…”

“…, where R ps = 120 Ω is the phase-slip line resistance, V s = 2.7 mV is the voltage switching amplitude, and Λ Q = 200 nm is the charge imbalance distance 22 . We conclude that the nanowire will switch into the resistive state after a single-escape event because Q n > 0.8382 and the tunneling from different energy levels can be detected by measuring the switching current.…”

“…The following parameters were used for the capacitance calculations: spacing S = 200 nm, substrate thickness H = 1 mm, and dielectric index of the STO substrate ε = 300. The spacing S consisted of the 60-nm-wide FIB cut and two 70-nm-wide damaged insulating regions of YBCO on the sides of the FIB cut 22 . By using the coplanar waveguide calculator 54 , we obtained a nanowire specific capacitance per unit length of C S = 2.4 fF μm −1 and a total capacitance of the 2-μm-long nanowire of C = 4.8 fF.…”

Charging of Superconducting Layers in Arrays of Coupled Josephson Junctions for Overcritical Currents

“…As a result, branching appears for overcritical currents in the IV-characteristic. Similar branching for overcritical currents has been experimentally observed by M. Lyatti, et al, in ultrathin high-T c superconducting YBCO nanowires [32] and nanobridges [33]. Our result was derived from numerical simulations of a stack of coupled Josephson junctions in the framework of a capacitively coupled Josephson junctions with diffusion current (CCJJ + DC) model, described in Section 2.…”

“…The existence of an additional branching for currents greater than the critical one was clearly identified by M. Liatty et al [32]. From Figure 4 of the mentioned article [32], it can be clearly seen that the voltage jumps similar to the transitions BC and DA from Figure 1 of our article. Because points A and B correspond to different currents, hysteresis appears.…”