Universal resistance capacitance crossover in current-voltage characteristics for unshunted array of overdamped Nb–AlOx–Nb Josephson junctions

Abstract

Compression of a magnetic flux in the intergrain medium of a YBa2Cu3O7 granular superconductor from magnetic and magnetoresistive measurements J. Appl. Phys. 110, 093918 (2011) Quantum phase dynamics in an LC shunted Josephson junction J. Appl. Phys. 109, 093915 (2011) Array of Josephson junctions with a nonsinusoidal current-phase relation as a model of the resistive transition of unconventional superconductors J. Appl. Phys. 108, 123916 (2010) Preparation of overdamped NbTiN Josephson junctions with bilayered Ti-TiN barriers J. Appl. Phys. 108, 113904 (2010) Exact analytical solution of a classical Josephson tunnel junction problem Low Temp. Phys. 36, 1012Phys. 36, (2010 Additional information on J. Appl. Phys. Among many different properties which can be studied using highly ordered two-dimensional ͑2D͒ arrays of Josephson junctions probably one of the most interesting ͑and important for their potential applications͒ is their transport behavior, reflecting manifestation of numerous dissipation mechanisms in the arrays ͑see, e.g., Refs. 1-3 and further references therein͒ via nonlinear current-voltage characteristics ͑CVC͒ of the general form V ϰ ͓I − I C ͑T͔͒ a͑T͒ with a power exponent a ranging from a Ͻ 1 to a Ͼ 1 depending on the particular mechanism and collateral effects ͑such as finite size of the single junction and/or the array, thermal fluctuations, quasiparticle contributions, etc.4-9 ͒. At the same time, recall that only sufficiently overdamped Josephson junctions ͑with nonhysteretic CVC͒ and their arrays can be effectively used in rapid single flux quantum logic circuits and programmable Josephson voltage standards ͑see, e.g., Refs. 10-13 and further references therein͒. In this paper we report our results on CVC for superconductor-insulator-superconductor ͑SIS͒ type array of strongly overdamped Nb-AlO x -Nb junctions at different temperatures. We observed quite a pronounced crossover at some current I cr = ͑1 / 2␤ C −1͒I C between a resistance R dominated state ͑below I cr ͒ and a capacitance C dominated state ͑above I cr ͒ which could be utilized as a versatile resistance-capacitance ͑R-C͒ switch within Josephson electronics. High quality ordered SIS type unshunted array of overdamped Nb-AlO x -Nb junctions has been prepared by using a standard photolithography and sputtering technique. [16][17][18][19][20] because of the well-defined periodic structure of our array, it is reasonable to expect that our experimental results can be quite satisfactory explained by analyzing the dynamics of a single unit cell of the array. In our calculations, the unit cell is a plaquette containing four identical Josephson junctions. By analogy with the resistively shunted junction ͑RSJ͒ model, 9 the total current in the plaquette readsHere i ͑t͒ is the gauge-invariant superconducting phase difference across the ith junction, and ⌽ 0 is the magnetic flux quantum. For any particular solution i ͑t͒ of this equation at I 0, the resulting CVC of the RSJ model is given by the time average of the voltage ͑ ...

Manifestation of geometric resonance in current dependence of AC susceptibility for unshunted array of Nb–Alx–Nb Josephson junctions

“…The critical current for the junctions forming the array is I C (T) = 150 lF at T = 4.2 K. Given the values of the junction quasi-particle resistance R = 10 X, inductance L = l 0 a = 64 pH, and capacitance C = 1.2 fF, the geometrical and dissipation parameters are estimated to be b L (T) = 2pLI C (T)/U 0 = 30 and b C (T) = 2pCR 2 I C (T)/ U 0 = 0.05 at T = 4.2 K, respectively. The latter estimate suggests that our array can be effectively used, for example, in rapid single flux quantum logic circuits and programmable Josephson voltage standards [20,21].…”

“…2 for the sketch of the setup used in the present experiments). The measurements of CVC V(I) were made using homemade experimental technique with a high-precision nanovoltmeter [21][22][23]. Some typical results for the obtained V(I) dependencies in our array (taken at two distinctive temperatures and exhibiting a noticeable nonlinear behavior) are shown in Fig.…”

Josephson Junction, the Quantum Engine: from S.QU.I.D. Sensors to Qubits for Quantum Computers

“…However, for a more adequate description of the flux dynamics in truly 2D systems, these effects should be considered. Indeed, as accurate numerical simulations have revealed, both self-inductance and mutual inductance effects will have a significant impact on the array's dynamic properties through the creation of rather strong self-induced magnetic fields [26].…”

On the field-induced diaelastic effect in a small Josephson contact

“…In particular, a remarkable increase of the measurements technique resolution made it possible to experimentally detect such inter esting phenomena as flux avalanches [5], geometric quantization [6], flux driven oscillations of heat capacity [7], reentrant like behavior [8], manifesta tion of π contacts [9], R-C crossover [10], unusually strong coherent response [11], Josephson analog of the fishtail effect [12], geometric resonance and field induced Kosterlitz-Thouless transition [13]. Among the numerous theoretical predictions (still awaiting their experimental verification) one could mention electro and magnetostriction [14], field induced polarization effects [15], analog of magnetoelectric effect [16], nonlinear Seebeck effect and thermal con ductivity [17], stress induced effects [18], chemomag netism [19], magnetoinductance effects [20], implica tions of dipolar interactions for wireless connection between Josephson qubits [21] and for weakening of the Coulomb blockade [22], proximity induced superconductivity in graphene [23] and anomalous Josephson current in topological insulators [24].…”